I dunno, I think SOM is way more interesting. I didn't realize XNA was so messed up that way. I'm not sure C# is such a problem to port to, and C# can be very flexible, if C# would be the onliy requirement. I know Torque was converting it's tools into XNA, so it's not so much that you have to use a specific "game engine" setup, though I'm sure there is a bit of that. 150mb is not so hard at all. I can easily program an extension for SOM to use mpg music instead of wav, which should cut the soundtrack download size down greatly. Though I'm thinking that 150mb is the download and not the install size. A SOM game could easily fit in under that. We could technically make it open source I'd think by calling SOM a data file, and mapping it into memory and executing it from there. But that probably would not pass thru the gatekeepers... possibly even if Fromsoftware and Agetec gave everything the go ahead.
Given the dead in the water status of KF, it might be possible to even convince Agetec and Fromsoftware let us go forward. I think the Opensource bit is actually in our favor. I'm actually shocked about that. Though I reckon it's more you gotta turn over sources to MS than have your sources available for the world to see online. Trying to convince the whole world to go opensource games I considered to be my greatest hurdle... it will be interesting if these "indie" game network things the major gatekeepers are doing already have that concept built in.
I thought about joining (the no fee way) one day while I ran into the forums while Googling, but their registration process was messed up that day (I got an email letting me know it was fixed) ...all I've really thought about it was it's the only way to publish an Xbox game without buying a dev package/license.