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Long before the term "Open Source" was used, software was developed by loose associations of programmers and freely exchanged. Starting in the early 1950's, organizations such as http://www.share.org[SHARE] and http://www.decus.org[DECUS] developed much of the software that computer hardware companies bundled with their hardware offerings. At that time computer companies were in the hardware business; anything that reduced software cost and made more programs available made the hardware companies more competitive.
In the mid-1980s a government anti-trust case against AT&T ended with the break-up of AT&T. AT&T still owned Unix and was now able to sell it. AT&T embarked on an aggressive licensing effort and most commercial Unixes of the day became AT&T-derived.
In the early 1990's AT&T sued UCB over license violations related to BSD. UCB discovered that AT&T had incorporated, without acknowledgment or payment, many improvements due to BSD into AT&T's products, and a lengthy court case, primarily between AT&T and UCB, ensued. During this period some UCB programmers embarked on a project to rewrite any AT&T code associated with BSD. This project resulted in a system called BSD 4.4-lite (lite because it was not a complete system; it lacked 6 key AT&T files).
In the mid 1990s, Novell purchased AT&T's Unix rights and a (then secret) agreement was reached to terminate the lawsuit. UCB soon terminated its support for BSD.
Do not confuse the new BSD license with "public domain". While an item in the public domain is also free for all to use, it has no owner.
"This General Public License does not permit incorporating your program into proprietary programs."<<one>>
The http://www.opensource.org/licenses/gpl-license.php[GPL] is a complex license so here are some rules of thumb when using the GPL:
the rule-of-thumb states that if GPL source is required for a program to compile, the program must be under the GPL. Linking statically to a GPL library requires a program to be under the GPL.
the GPL requires that any patents associated with GPLed software must be licensed for everyone's free use.
simply aggregating software together, as when multiple programs are put on one disk, does not count as including GPLed programs in non-GPLed programs.
output of a program does not count as a derivative work. This enables the gcc compiler to be used in commercial environments without legal problems.
since the Linux kernel is under the GPL, any code statically linked with the Linux kernel must be GPLed. This requirement can be circumvented by dynamically linking loadable kernel modules. This permits companies to distribute binary drivers, but often has the disadvantage that they will only work for particular versions of the Linux kernel.
Due in part to its complexity, in many parts of the world today the legalities of the GPL are being ignored in regard to Linux and related software. The long-term ramifications of this are unclear.
The origins of Linux and the LGPL
While the commercial Unix wars raged, the Linux kernel was developed as a PC Unix clone. Linus Torvalds credits the existence of the GNU C compiler and the associated GNU tools for the existence of Linux. He put the Linux kernel under the GPL.
Remember that the GPL requires anything that statically links to any code under the GPL also be placed under the GPL. The source for this code must thus be made available to the user of the program. Dynamic linking, however, is not considered a violation of the GPL. Pressure to put proprietary applications on Linux became overwhelming. Such applications often must link with system libraries. This resulted in a modified version of the GPL called the http://www.opensource.org/licenses/lgpl-license.php[LGPL] ("Library", since renamed to "Lesser", GPL). The LGPL allows proprietary code to be linked to the GNU C library, glibc. You do not have to release the source code which has been dynamically linked to an LGPLed library.
If you statically link an application with glibc, such as is often required in embedded systems, you cannot keep your application proprietary, that is, the source must be released. Both the GPL and LGPL require any modifications to the code directly under the license to be released.
Open Source licenses and the Orphaning Problem
One of the serious problems associated with proprietary software is known as "orphaning". This occurs when a single business failure or change in a product strategy causes a huge pyramid of dependent systems and companies to fail for reasons beyond their control. Decades of experience have shown that the momentary size or success of a software supplier is no guarantee that their software will remain available, as current market conditions and strategies can change rapidly.