Honestly, It's fine if people make mario clones.
It's just important that they have IDEAS.
Imagine how many great programmers are just doing nothing right now, because they don't have any ideas.
Once you get started, you can change the theme of the game without starting over, if you decide to do something more creative.
An encryptor would probably be better than a compressor. If SB finds the compressor, they could easily decompress the programs created with it. However, with the programs being encrypted with a password, they would also need the password to decrypt it. Said password would be shared along with the public key (and likely instructions to decrypt it, i.e. how to download and use the decryptor). I'd recommend the program generate it's own encryption password (in a similar fashion to the public keys) which would be printed back to the user, but still allow the user to manually choose a password. This way, users wouldn't be inconvenienced by having to choose their own password.
Mario physics fine, but NOT Mario. Use the default sprites or make your own. Don't steal, don't dodge rules.
I still don't see why we want to cheat the system. If the US version users are causing infringement trouble, SB will most certainly think twice about an EU release. Kobayashi said as much on twitter -- the US user base and activity will be one indicator for their EU release decision.
As I've said before, the main purpose of a compressor/encryptor shouldn't be to dodge copyright; it has far more legitimate applications than that.
Also, do you guys seriously think SmileBoom really cares enough to manually check offending content and figure out how it dodged the system? They don't. They only really manually remove anything if they know about, they don't go looking.
I really wish I hadn't suggested the encryption idea...
This is why I wish hadn't suggested the idea...
A compressor would be nice for petit modem, though.