Jim is making the code freely available, it's hosted on github and it's easy to see. What Jim hasn't made available is anything containing Williams IP, such as sounds, DMD animations and so on. With P-ROC development, those are kept in separate files (so sounds will be regular old .wav or .mp3 files, for example) which he has chosen not to make publicly available.
So long as it stays that way, PPS / Williams won't have any issue since it's his machine to do what he wants with. The rules of the game themselves are not subject to IP, just the sound, animation and artwork. If Jim decides in the future to make the whole thing available, he'll either need to work with PPS, or replace the Williams IP with something else.