Hello.
I've written a GPLed (not LGPLed) library which I know is currently used in a software licensed under the BSD license, so this is clearly a GPL violation since the other software license should be GPLed too.
That's not completely right, as already remarked by Tomasz Wegrzanowski.
The program as a whole must be licensed according to GPL terms, but each part (file or whatever) can still be licensed in a different way as long as it's a gpl-compatible license.
Thus, your used can't distribute the binary unless on GPL terms, but some parts can be reused according to different terms.
However, please be careful when talking about "BSD" license, as there's not one of such licenses. http://www.gnu.org/philosophy/bsd.html explains why it is unclear to talk about BSD-style licenses.
I'm currently trying to make the other software authors change their license to GPL to comply with my module's license.
It's not needed. But the program _as_a_whole_ must be GPL'd if they include your code.
However AFAIK it may be impossible for them to comply since they may be disallowed to do so by the company they are a part of, which may want to keep the right to close their sources (we are currently discussing the issue, no need for a flamewar on them)
They can close their source, but not link them with your library in that case. So they don't need to change license to use your library in the free release; they just won't be able to use the library in a non-free release.
In other words, in the worst case scenario, the two only options available to them are :
1 - don't use my library at all.
2 - ask me for a sublicense in exchange of money (I'm the only author), which I'd be glad to accept ;-)
I've had the same problem. We (several authors) would accept to release LGPL if paid to do do. The "client" turned to a different (proprietay) product instead.
Now if they finally choose point 2, and ask for my software under a different license (BSD for example) and I agree, what are my options to :
1 - give them my software under the BSD license in exchange of money.
Yes. Why still releasing to the public the GPL version. Sure people can distribute the BSD version, but if yours is the "official" one you most likely won't loose control of it. But yes, having to "competitors" in this way might be very bad to handle.
2 - allow them to give/resell and/or close their sources which include my own BSDized (or other) sources.
You might give them a copy with a different license, still not BSD, that they could use in the non-free version. They should have no problem in linking the GPL library from the free distribution.
3 - don't allow any of their "client" to extract my library's sources from their whole package and redistribute it under the BSD license, since I want to keep my library under the GPL for the rest of the world.
That's whay I say above, but your terms are wrong. IF there's such clause than it's not BSD at all.
Hope this helps
I've asked to the FSF but I've got no answer yet.
Sorry, we are very backlogged.
/alessandro