Why is it not clear? You pay for the license. The license grants you the right to use the binaries, and to inspect and modify the source code. If you don't pay for the license, then you do not have the right to use the binaries or to inspect and modify the source code. So anybody who possesses binaries and/or source code and can't prove that they legally obtained them (by paying the license fee) is in violation of the license. It's exactly the same as with closed source software, only here you get the additional right to use the source code any way you please.