Then don't use it.

You have no right to permissively licensed code.

I should have explained the context of the idea. I just wanted to sell a tool for my cms (locomotivecms). This tool happens to be a ruby script which is regularly updated and that I want to sell to "finance" the cms (free of charge since it's an open source project). And the best way I found is to sell it as a ruby gem so that the installation / update become easy for the ruby users.

By the way, the code is not obfuscated. So yes, basically, users who paid for the gems can put this in their own git repository and do "whatever" they want with it as long as they don't share it.

Does it make sense ?