It appears this article is grossly out of date (April 22, 200), nearly four years old.
The SharkyExtreme article mentions "Up to eight games can be made available at any one time to players". But I believe this is no longer true. I think you can select any game installed now.
Also it appears that Ultracade has redesigned their website. Much better, and it shows some new products such as the Dragon's Lair & Space Ace cabinets.
There is a brief history of Ultracade on thier site (only up to 2002 though), and it mentions the acquisition of Hyperware's emulator in 1997, so that must be the emulator they are using underneath (not MAME or "ripped" MAME code). It also mentions that Ultracade was split off from Quantum3D in 2002 (another place where the article's info is lacking). Also, it's interesting to note that Ultracade got it's roots in 3DFx (as same people started Quantum3D later), and 3DFx got it's start in the arcade hardware industry. They've come full circle now.