BSD/GPL compatibility is a complex issue. Here's my take. The 2/3 clause BSD licenses are clearly compatible with the GPL v2 because they offer a strict super

BSD/GPL compatibility is a complex issue. Here's my take. The 2/3 clause BSD licenses are clearly compatible with the GPL v2 because they offer a strict superset of rights. I.e. they don't offer any restrictions not found in the GPL v2. Consequently the work as a whole can be licensed under the GPL v2 without worrying about whether any piece of it has additional permissions which satisfy the license. The GPL v3 however provides some real reasons for caution here. The additional permission section is clearly compatible with the MIT license, but is clearly incompatible, as it stands, with the BSD license which does not explicitly grant sublicensing rights (meaning you can't relicense someone else's BSD code under the GPL without their permission). So you can't include BSD licensed code and count on the additional permissions section as protecting you. (This is based on my discussions with Richard Fontana and other lawyers involved in free software issues.) The question then becomes whether section 7(b) legal notices can be read broadly enough to include the BSD license. I.e. the author of the BSD licensed code is merely giving notice that all users have the permission, directly from him, to use the code as allowed under the BSD license. This is not an additional permission under the GPL, but an additional permission directly from the author, and notice is merely being preserved. If this is the case, then the GPL v3 is compatible with BSD licenses which do not have an obnoxious advertising clause. But if it is not, and if all additional permissions must be removable even in the absence of software modification, then they are incompatible.