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Berkley Software Distribution (BSD)
Berkeley Software Distribution (BSD) is the UNIX derivative distributed by the University of California, Berkeley starting in the 1970s. The name is also used collectively for the modern descendants of these distributions.
BSD pioneered many of the advances of modern computing. Berkeley's Unix was the first to include library support for the IP stacks, Berkeley sockets. By integrating sockets with the UNIX operating system file descriptors, users of their library found it almost as easy to read and write data across the network, as it was to put data on a disk.
The AT&T laboratory eventually released their own STREAMS library, which incorporated much of the same functionality in a software stack with better architectural layers, but the already widely-distributed sockets library, together with the unfortunate omission of a function call for polling a set of open sockets (an equivalent of the select call in the Berkeley library), made it difficult to justify porting applications to the new API.
Today, it continues to be used as technology testbed by academic organizations, as well as high-technology examples in a lot of commercial and free products. It is increasingly being used on embedded devices as well. The general quality of its source code design and clean writing, as well as its documentation (especially reference manual pages, commonly referred to as "man pages"), make such systems a heaven for programmers.
It is an interesting fact that BSD operating systems can run native software of several other operating systems on the same architecture, using binary compatibility. This, much faster than emulation, allows for instance to run applications intended for Linux on a BSD operating system at full speed. This makes BSD not only suitable for server environments, but also for workstation ones, considering the increasing availability of commercial or closed-source software for Linux. It also allows to migrate old commercial software which only used to run on commercial UNIX platforms to a modern BSD operating system, while retaining functionality of the previous system until it can fully be replaced by a better alternative.
Like AT&T Unix, the BSD kernel is monolithic, meaning that device drivers in the kernel run in privileged mode, as part of the core of the operating system. Early versions of BSD were used to form Sun Microsystems' Sun OS, founding the first wave of popular Unix workstations.
The GNU General Public License (GNU GPL or simply GPL) is a free software license, originally written by Richard Stallman for the GNU project (a project to create a complete free software OS). It has since become the most popular license for free software (or "open source software"). The latest version of the license, version 2, was released in 1991.
The GPL grants the recipients of a computer program the following rights, or "freedoms":
(a) The freedom to run the program, for any purpose.
(b) The freedom to study how the program works, and modify it. (Access to the source code is a precondition for this)
(c) The freedom to redistribute copies.
(d) The freedom to improve the program, and release the improvements to the public. (Access to the source code is a precondition for this)
In contrast, the end user license that come with proprietary software rarely grant the end user any rights (other than the right to use the software, although it is debatable whether one requires a license for use per se), and may even attempt to restrict activities normally permitted by law, such as reverse engineering.
The primary difference between the GPL and more "permissive" free software licenses such as the BSD license is that the GPL seeks to ensure that the above freedoms are preserved in copies and in derivative works. It does this using a legal mechanism known as copyleft, invented by Stallman, which requires derivative works of GPL-licensed programs to also be licensed under the GPL. In contrast, BSD-style licenses allow for derivative works to be redistributed as proprietary software.
By some measures, the GPL is the single most popular license for free and Open Source software. As of April 2004, the GPL accounted for nearly 75% of the 23,479 free-software projects listed on Freshmeat, and about 68% of the projects listed on SourceForge. (It should be noted that these two sites are owned by OSTG, a company that advocates Linux and the GPL).
The GPL does not give the licensee unlimited redistribution rights. The right to redistribute is granted only if the licensee includes the source code (or a legally-binding offer to provide the source code), including any modifications made. Furthermore, the distributed copies, including the modifications, must also be licensed under the terms of the GPL.
This requirement is known as copyleft, and it gets its legal teeth from the fact that the program is copyrighted. Because it is copyrighted, a licensee has no right to modify or redistribute it (barring fair use), except under the terms of the copyleft. One is only required to accept the terms of the GPL if one wishes to exercise rights normally restricted by copyright law, such as redistribution. Conversely, if one distributes copies of the work without abiding by the terms of the GPL (for instance, by keeping the source code secret), they can be sued by the original author under copyright law.
Many distributors of GPL'ed programs bundle the source code with the executables. An alternative method of satisfying the copyleft is to provide a written offer to provide the source code on a physical medium (such as a CD) upon request. In practice, many GPL'ed programs are distributed over the Internet, and the source code is made available over FTP. For Internet distribution, this complies with the license.
The copyleft only applies when a person seeks to redistribute the program. One is allowed to make private modified versions, without any obligation to divulge the modifications as long as the modified software is not distributed to anyone else. Note that the copyleft only applies to the software and not to its output (unless that output is itself a derivative work of the program); for example, a web portal running a modified GPL content management system is not required to distribute its changes to the underlying software. (It has been suggested that this be changed for version 3 of the GPL).
Berkeley Software Distribution (BSD) is the UNIX derivative distributed by the University of California, Berkeley starting in the 1970s. The name is also used collectively for the modern descendants of these distributions.
BSD pioneered many of the advances of modern computing. Berkeley's Unix was the first to include library support for the IP stacks, Berkeley sockets. By integrating sockets with the UNIX operating system file descriptors, users of their library found it almost as easy to read and write data across the network, as it was to put data on a disk.
The AT&T laboratory eventually released their own STREAMS library, which incorporated much of the same functionality in a software stack with better architectural layers, but the already widely-distributed sockets library, together with the unfortunate omission of a function call for polling a set of open sockets (an equivalent of the select call in the Berkeley library), made it difficult to justify porting applications to the new API.
Today, it continues to be used as technology testbed by academic organizations, as well as high-technology examples in a lot of commercial and free products. It is increasingly being used on embedded devices as well. The general quality of its source code design and clean writing, as well as its documentation (especially reference manual pages, commonly referred to as "man pages"), make such systems a heaven for programmers.
It is an interesting fact that BSD operating systems can run native software of several other operating systems on the same architecture, using binary compatibility. This, much faster than emulation, allows for instance to run applications intended for Linux on a BSD operating system at full speed. This makes BSD not only suitable for server environments, but also for workstation ones, considering the increasing availability of commercial or closed-source software for Linux. It also allows to migrate old commercial software which only used to run on commercial UNIX platforms to a modern BSD operating system, while retaining functionality of the previous system until it can fully be replaced by a better alternative.
Like AT&T Unix, the BSD kernel is monolithic, meaning that device drivers in the kernel run in privileged mode, as part of the core of the operating system. Early versions of BSD were used to form Sun Microsystems' Sun OS, founding the first wave of popular Unix workstations.
The GNU General Public License (GNU GPL or simply GPL) is a free software license, originally written by Richard Stallman for the GNU project (a project to create a complete free software OS). It has since become the most popular license for free software (or "open source software"). The latest version of the license, version 2, was released in 1991.
The GPL grants the recipients of a computer program the following rights, or "freedoms":
(a) The freedom to run the program, for any purpose.
(b) The freedom to study how the program works, and modify it. (Access to the source code is a precondition for this)
(c) The freedom to redistribute copies.
(d) The freedom to improve the program, and release the improvements to the public. (Access to the source code is a precondition for this)
In contrast, the end user license that come with proprietary software rarely grant the end user any rights (other than the right to use the software, although it is debatable whether one requires a license for use per se), and may even attempt to restrict activities normally permitted by law, such as reverse engineering.
The primary difference between the GPL and more "permissive" free software licenses such as the BSD license is that the GPL seeks to ensure that the above freedoms are preserved in copies and in derivative works. It does this using a legal mechanism known as copyleft, invented by Stallman, which requires derivative works of GPL-licensed programs to also be licensed under the GPL. In contrast, BSD-style licenses allow for derivative works to be redistributed as proprietary software.
By some measures, the GPL is the single most popular license for free and Open Source software. As of April 2004, the GPL accounted for nearly 75% of the 23,479 free-software projects listed on Freshmeat, and about 68% of the projects listed on SourceForge. (It should be noted that these two sites are owned by OSTG, a company that advocates Linux and the GPL).
The GPL does not give the licensee unlimited redistribution rights. The right to redistribute is granted only if the licensee includes the source code (or a legally-binding offer to provide the source code), including any modifications made. Furthermore, the distributed copies, including the modifications, must also be licensed under the terms of the GPL.
This requirement is known as copyleft, and it gets its legal teeth from the fact that the program is copyrighted. Because it is copyrighted, a licensee has no right to modify or redistribute it (barring fair use), except under the terms of the copyleft. One is only required to accept the terms of the GPL if one wishes to exercise rights normally restricted by copyright law, such as redistribution. Conversely, if one distributes copies of the work without abiding by the terms of the GPL (for instance, by keeping the source code secret), they can be sued by the original author under copyright law.
Many distributors of GPL'ed programs bundle the source code with the executables. An alternative method of satisfying the copyleft is to provide a written offer to provide the source code on a physical medium (such as a CD) upon request. In practice, many GPL'ed programs are distributed over the Internet, and the source code is made available over FTP. For Internet distribution, this complies with the license.
The copyleft only applies when a person seeks to redistribute the program. One is allowed to make private modified versions, without any obligation to divulge the modifications as long as the modified software is not distributed to anyone else. Note that the copyleft only applies to the software and not to its output (unless that output is itself a derivative work of the program); for example, a web portal running a modified GPL content management system is not required to distribute its changes to the underlying software. (It has been suggested that this be changed for version 3 of the GPL).
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