fostering the non-commercial game developer community is a great idea. however I think it would be more effective if you:
1) allow sharing of binary versions of the games.
2) provide a place on XBL where developers can publish their games (in binary and/or source form, possibly with gotdotnet-style source control). build a community around the games: high-scores, forums, multiplayer, etc...
3) prodive a cheaper 'read-only' membership to the XNA club so non-developers can enjoy these homebrew games.

How to ensure that XNA succeeds
Renan Souza