I have the XNA developer kit. I dicked around with it for about a year, and ended up with a few side scrolling test levels. Nothing at all worth anything. Basically spent time reverse-engineering templates. It was more of a learning process. Fun though. I am still waiting for Magic to send me fighting poses of himself so I can attempt making a fighting game...
There MUST be a skate game for PC. I am not sure what open-source developer software is best, but I know there is a ton of free shit out there. At the very least, some of us could pool our resources and make a room with a fun box and a skater that moves around. If we made it that far, we'd have a better understanding of what it would take to continue pursuing it.
If a forum community can develop a fully functioning 3d printer http://www.reprap.org/wiki/Main_Page, one can make a skateboarding game. Fuck anyone who thinks it's not possible.
I also have some contacts in app development. I'll poke around.