Is there MAME for preware?
Yes but it's still in the development stages. The developer is willing to add iCade support and seems to be trying to do it, but it's complicated by the fact that he doesn't own the iCade. :-/
See the thread here: http://forums.webosn...l-touchpad.html
The last half of page 2 and page three are mostly devoted to the developer communicated with people with iCades and trying to get a handle on how it works. Cross your fingers that he can make it work.
As for other WebOS apps that support the iCade, so far as far as I am aware only No Gravity does. I can personally vouch that it does work with the iCade paired to the Touchpad in WebOS.
The developer for Starstation Quixotic does own the iCade and has stated in a thread at WebOSNation that he will be adding iCade support in a future update for the game.
Also note that the iOS version of both No Gravity and Starstation Quixotic currently support iCade and are available in the Apple app store.