@lanodan @sjw Yeah, I mean, my point is that a codebase's status is independent of the purported licensing. I think the distinction matters a great deal here if they are talking about patents.

> the explicit patent requirement *in* the license restricts the fields of endeavour clause,

That makes sense. It's not going to be GPL-compatible for that reason, I can see an argument that it doesn't qualify as free software at all. I think it gets around it by saying "Maybe some patent licensing is required. No patent license grants are provided." Like, I could release some software and license it under the FDK and as long as I did not actually publish any patented software under that license, it would be a free codebase. The AT&T Public License granted a patent license but revoked it if you modified the code: the patents being asserted in the license and the different status if the user modifies it are probably the reasons. You lose rights that you were granted for altering the code. The FDK doesn't grant any of those rights and doesn't assert them or revoke them: it just suggests that you apply for a patent license. The GPLv3 requires a patent grant but the GPLv2 had this in the preamble:

> Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.