Licensing
A goal of the OpenBSD project is to "maintain the spirit of the original Berkeley Unix copyrights", which permitted a "relatively un-encumbered Unix source distribution". To this end, the Internet Systems Consortium (ISC) licence, a simplified version of the BSD licence with wording removed that is unnecessary under the Berne convention, is preferred for new code, but the MIT or BSD licences are accepted. The widely used GNU General Public License is considered overly restrictive in comparison with these.
In June 2001, triggered by concerns over Darren Reed's modification of IPFilter's licence wording, a systematic licence audit of the OpenBSD ports and source trees was undertaken. Code in more than a hundred files throughout the system was found to be unlicensed, ambiguously licensed or in use against the terms of the licence. To ensure that all licences were properly adhered to, an attempt was made to contact all the relevant copyright holders: some pieces of code were removed, many were replaced, and others, including the multicast routing tools, mrinfo and map-mbone, which were licensed by Xerox for research only, were relicensed so that OpenBSD could continue to use them; also removed during this audit was all software produced by Daniel J. Bernstein. At the time, Bernstein requested that all modified versions of his code be approved by him prior to redistribution, a requirement to which OpenBSD developers were unwilling to devote time or effort. The removal led to a clash with Bernstein who felt the removal of his software to be uncalled for. He cited the Netscape web browser as much less freely licensed and accused the OpenBSD developers of hypocrisy for permitting Netscape to remain while removing his software. The OpenBSD project's stance was that Netscape, although not open source, had licence conditions that could be more easily met. They asserted that Bernstein's demand for control of derivatives would lead to a great deal of additional work and that removal was the most appropriate way to comply with his requirements.
The OpenBSD team has developed software from scratch, or adopted suitable existing software, because of licence concerns. Of particular note is the development, after licence restrictions were imposed on IPFilter, of the pf packet filter, which first appeared in OpenBSD 3.0 and is now available in DragonFly BSD, NetBSD and FreeBSD. OpenBSD developers have also replaced GPL licensed tools (such as diff, grep and pkg-config) with BSD licensed equivalents and founded new projects including the OpenBGPD routing daemon and OpenNTPD time service daemon. Also developed from scratch was the globally used software package OpenSSH.
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