There are GPL licensed ROM images. Debian ships them for ZX Spectrum emulators, where the copyright holder (British Sky Broadcasting) makes other versions available only under effectively NC-ND terms. Instead Debian was able to convince the original development team of the benefits. I don't believe this is an isolated case either.
- Re: [GNU-linux-libre] MAME Denis 'GNUtoo' Carikli
- Re: [GNU-linux-libre] MAME J.B. Nicholson
- Re: [GNU-linux-libre] MAME Felipe Sanches
- Re: [GNU-linux-libre] MAME Julian Marchant
- Re: [GNU-linux-libre] MAME J.B. Nicholson
- Re: [GNU-linux-libre] MAME rain1
- Re: [GNU-linux-libre] MAME Felipe Sanches
- Re: [GNU-linux-libre] MAME Jason Self
- Re: [GNU-linux-libre] MAME Felipe Sanches
- Re: [GNU-linux-libre] MAME Julian Marchant
- Re: [GNU-linux-libre] MAME Matt Lee
- Re: [GNU-linux-libre] MAME Luke
- Re: [GNU-linux-libre] MAME Jean Louis
- Re: [GNU-linux-libre] MAME Felipe Sanches
- Re: [GNU-linux-libre] MAME Felipe Sanches
- Re: [GNU-linux-libre] MAME Jean Louis
- Re: [GNU-linux-libre] MAME Jason Self
- Re: [GNU-linux-libre] MAME Denis 'GNUtoo' Carikli
- Re: [GNU-linux-libre] MAME Denis 'GNUtoo' Carikli
- Re: [GNU-linux-libre] MAME Joshua Gay
- Re: [GNU-linux-libre] MAME J.B. Nicholson