Copyright law is complex, OpenBSD policy is simple - OpenBSD strives to maintain the spirit of the original Berkeley Unix copyrights.
The Berkeley copyright poses no restrictions on private or commercial use of the software and imposes only simple and uniform requirements for maintaining copyright notices in redistributed versions and crediting the originator of the material only in advertising.
While this means that OpenBSD is has the same broad applicability as the material it was derived from, it also follows that OpenBSD can not include some material which includes more restrictive copyrights, or must limit it's scope - for example GPL style copyrights are not acceptable for inclusion in the kernel or what would constitute a "binary release" of OpenBSD.
Copyright law admits to three general categories of works:
It is vitally important to understand that copyrights are broad protections as defined by national and international copyright law, not assertions of the copyright holder as to what might or might be copyrighted, nor the conditions for use imposed by the copyright holder.
Again, the important points to note are that the release and conditions can only apply to the portion of the work that was originated by the copyright holder - the holder of a copyright on a derivative work can neither grant additional permissions for the original work, nor impose more restrictive conditions for that work.
When a party asserting copyright rights removes prior copyright notices or releases from a work, or attempts to impose permissions or conditions that are in conflict with the permissions or conditions imposed by the originator of the work, these conditions are not binding on the original work. In fact, if their permissions or conditions are contrary to those asserted by the copyright holder of the original work, that party is probably setting up a situation where they no longer have permission to use the work at all, let along impose conditions on its use.
Finally, releases are generally binding on the material that they are distributed with. This means that if the originator of a work distributes that work with a release granting certain permissions, those permissions apply as stated, without discrimination, to all persons legitimately possessing a copy of the work. That means that having granted a permission, the copyright holder can not retroactively say that an individual or class of individuals are no longer granted those permissions. Likewise should the copyright holder decide to "go commercial" he can not revoke permissions already granted for the use of the work as distributed, though he may impose more restrictive permissions in his future distributions of that work.
This section attempts to summarize the position of OpenBSD relative to some commonly encountered copyrights.
The Berkeley copyright is the model for the OpenBSD copyright. It retains the rights of the copyright holder, while imposing minimal conditions on the use of the copyrighted material. Material with Berkeley copyrights, or copyrights closely adhering to the Berkeley model can generally be included in OpenBSD.
While AT&T holds the copyrights to much "unix" code and documentation, OpenBSD is based largely on Berkeley (BSD) distributions that contain only material known to be free of AT&T copyrights, or material to which AT&T has abandoned it's copyright or included licensing terms similar to the Berkeley terms. No material subject to restrictive AT&T copyrights can be included in OpenBSD.
In general OpenBSD does not include material copyrighted by manufacturers or software houses. Material may be included where the copyright owner has granted general permission for reuse without conditions, with terms similar to the Berkeley copyright, or where the material is the product of an employee and the employer's copyright notice is effectively releases any rights they might have to the work.
The Carnegie-Mellon copyright is similar to the Berkeley copyright, except that it requests that derivative works be made available to Carnegie-Mellon. Because this is only a request and not a condition, such material can still be included in OpenBSD. It should be noted that existing versions of Mach are still subject to AT&T copyrights, which prevents the general distribution of Mach sources.
The GNU Public License and licenses modeled on it impose the restriction that source code must be distributed or made available for all works that are derivatives of the GNU copyrighted code. While this may be a noble goal in terms of software sharing, it is a condition that is typically unacceptable for commercial use of software. As a consequence, software bound by the GPL terms can not be included in the kernel or "runtime" of of OpenBSD, though GPL tools may be included as development tools or as part of the system at are "optional" and where there is no adequate substitute.
Much of OpenBSD is largely based on NetBSD, since some of the OpenBSD developers were involved in the NetBSD project and the general NetBSD license terms are compatible with the Berkeley license and permit such use. Since that time, individuals associated with the NetBSD project or the "NetBSD Foundation" have inserted stricter conditions in the copyrights of parts of the NetBSD software. Regardless of the legality/propriety of these actions, material including such restrictive conditions or derived from that material subsequent to imposition of these restrictions can not be included in OpenBSD.
Most of FreeBSD is also based on Berkeley licensed material or include copyright notices based on the Berkeley model. Such material can be included in OpenBSD, while parts that are subject to GPL or various individual copyright terms can not be include in OpenBSD.
Most of Linux is subject to GPL style licensing terms and therefore can not be included in OpenBSD. Individual components may be eligible, subject to the terms of the originator's copyright notices. Note that Linux "distributions" may also be subject additional copyright claims of the distributing organization, either as a compilation or on material included that's not part of the Linux core.
Most "shareware" copyright notices impose conditions for redistribution, use or visibility that are at conflict with the OpenBSD project goals. Review on a case-by-case basis is required as to whether the wording of the conditions is acceptable in terms of conditions being requested vs. demanded and whether the spirit of the conditions is compatible with goals of the OpenBSD project.
While material that is truly entered into the "Public Domain" can be included in OpenBSD, review is required on a case by case basis. Frequently "public domain" assertion is made by someone who does not really hold all rights under Copyright law to grant that status, or there are a variety of conditions imposed on use. For a work to be truly in the "Public Domain" all rights are abandoned and it is offered without restrictions.