BSDaemons

By Sidney Cammeresi IV

Although BSD-derived operating systems have numerous differences from Linux, one of the most significant, is the difference in the license under which the operating systems are distributed. Although many people take the use of such "freeware" for granted, all users should be aware of the licensing terms of the software they use.

Linux is distributed under the GNU General Public License (GPL). This license is the same one used for the GNU "system," which includes packages such as the assembler, linker, and C compiler, as well as things like Emacs. Basically, the GPL allows free use, modification, and redistribution, but distributors are required to provide the source code with their distribution or a way to get it. Because users must release their changes as source code if they modify such a program, GPLed software is not used in proprietary software.

On the other hand, BSD-derived operating systems such as FreeBSD, NetBSD, and OpenBSD are distributed under their original Berkeley copyrights, with similar additional copyrights attached. This license, known as the BSD license, does not require that source be distributed with modified versions, and allows use, modification, and redistribution in any form. For this reason, BSD licensed software can be included in proprietary software. Examples of this kind of use include commercial derivatives of the original BSD code like BSDI, NeXTSTEP, and SunOS, as well as derivatives from more modern bases like RTMX O/S, which is derived from OpenBSD. BSD licenses impose at most two requirements on reuse of such code: attribution through preservation of the original copyright notices in documentation, and some require attribution in advertisements relating to the software.

Writing free software is fun, but having people use it is fun as well. If you are planning to write free software, you should be very aware of the licenses available under which you may distribute your work so that your software will be used in the ways you want.