Worst case with the copyright is to just include a copy of the license with the zip.
The problem with BSD/GPL code in the main Phobos is any D program will link with it, and thus the license goes viral to all D programs. But since this is just interface files, separate from the stdlib aside from sharing a distribution zip, no compiled code will be shoved into Phobos proper, the copyright restrictions shouldn't affect anyone who is not specifically using that library anyway. If we're concerned that merely importing the file may cause license taint, we could add pragma(msg, "License Taint Warning: etc.c.mylib is GPL licensed"); It just seems to me that as long as it is separate from Phobos, so it remains opt-in for each individual program, we shouldn't have anything to worry about. Somebody setting out to use the C library has to provide the DLLs himself, so he's already aware of the license.
