Your protection is useless and can be broken in several ways. The only way to keep your plugin private is not to share it with anyone else.
One way to break it:
1. Hook set_fail_state with orpheu.
2. Block the native call and print "yes man

" just for the laughs.
3. Profit???
Another thing, get_user_ip(0, ...) gets the ip from net_address so what you are doing there is set_cvar(net_address, get_cvar(net_address)). Very useful.
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