hi, I'm new here, but I have some comments:
First, a DS port is absolutely feasible. There's a well-supported, albeit unofficial SDK (devkitPro) which I'm sure can be used to port GE. To those concerned about legals, Nintendo can do NOTHING if you're developing using public available tools. What you can't do is release a game/app coded using the NitroSDK withoput a licence from nintendo.
Granted, telling people to buy a M3/Supercard just to play your games isn't really appealing, especially if you're trying to sell the game. One could ship a M3 with a microsd with your game, but that'd rise the price way too high.
And, AFAIK, there's no firmware update for the DS that prevents homebrew apps from running.
The Wii is a completely different thing, and those serious about developing indie games should do some research and try putting togheter a WiiWare project, you can even use Torque Game Engine for that. It's not as easy as GE, but it's just $150.
For those wondering who the hell am I, I'm a full time DS developer

I'm not a lawyer though, but I'm pretty sure that if you stick to free tools, Nintendo can't prevent you from running whatever you want on your console
