From the little digging around that I did with my F-14 "Second Sortie" (P-ROC) project, it's pretty much as folks above have said.
- For your own personal use, anything goes. It's your machine, do what you like with it.
- If you are looking to distribute the work (either selling it or giving it away) then it can't contain any of the original IP.
So if it has a DMD display, you shouldn't be distributing any of the original animations or frames. You also should not be distributing any of the original sounds / music for the machine. Artwork too - the cab on my F-14 Second Sortie has custom decals that are very clearly a copy of the original Williams ones with some colour changes. Again, for my personal use that's OK, but I won't be distributing the decals themselves or the graphics files (and I have already been asked to).
Even the name "F-14 Tomcat" is a trademark for Williams when associated with a pinball machine:
So in my case fortunately it won't be a consideration. Lots of websites with sounds that are free to use and redistribute, for example I'll be needing a bunch of missile sounds...
I'll have a DMD with either self-created animations or using work which is free to use, like this for example :
On a general note I can see both sides to the argument. Sharing a little DMD or sound work in a real niche of a few folks doesn't sound so bad. But if PPS hadn't taken up the gauntlet and become the licensee for Williams we wouldn't be enjoying the parts availability which has been happening over the last few years IMHO. I much prefer the current situation to the old one. YMMV.