I don't know why people insist on trolling the MAME license and claiming it's not valid and therefore taking that as meaning you can do what you want.
Based on actual legal advice I was given a while back.
1) If the MAME license is valid, then it's legally binding, and if you're to stay legal you must abide by it (ie no commercial use)
2) If the MAME license is NOT valid then the software cannot be used at all, by anybody (ie no commercial use)
At no point does either scenario result in MAME being free to use in a commercial environment. It's our software, and even if the license was deemed invalid the copyright of each component would be held by the authors of that component, who would need to grant you permission to use it (ie provide you with a valid license)
The ONLY correct answer to this question is 'buy the original game boards, and operate those in the cabinet'
If you want multi-games there are a handful of legal ones available (Namco's official Pacman Anniversary boards (
http://flyers.arcade-museum.com/?page=flyer&db=videodb&id=5833&image=1 )
Taito's official Qix / Space Invaders hybrid (
http://flyers.arcade-museum.com/?page=flyer&db=videodb&id=3576&image=1 )
The Donkey Kong 3-in-1 Namco put out (
http://flyers.arcade-museum.com/?page=flyer&db=videodb&id=4278&image=1 )
Konami 80's AC Special
and if you're not bothered about them actually being classic games, there are things like SemiCom's XESS New Revolution
The xx-in-1 boards, NeoGeo multicarts etc. are all unlicensed, and rather poor quality too, makes me cringe when I see somewhere running one and it attempts to play the Gyruss music. If you want to be 100% above board and legal you simply can't use them. If you don't care, that's your business and a risk you've decided to take, but bootlegs are bootlegs.