If I were to ever sell a homemade cabinet, this is how I would do it.
Build a cab with some sweet controls etc. make it really nice and unique looking. Buy some popular commercial computer games and get those all working good with the custom control panel. Package the cabinet with the commercial bought games. Then also, in the item's description mention that it could possibly be used with MAME, but not have it installed. Mention to them that there are literally THOUSANDS of people right now using this program called MAME that can be obtained online for FREE to play just about any and all classic video games from the past. Also mention that it is fairly easy to get working.
That is how I would approach the selling of a cabinet. My guess is you would be safe doing something like that. Also, search for the rules of the ability to even mention MAME in a commercial ad. There was a recent post in the MAIN forum discussing it. Follow MAME's rules and you should be set. Good Luck!