I hear Epic is pretty good about chasing down instances of plugin piracy, but unfortunately there really doesn’t appear to be a system in place to actually stop it before it happens.
Even stuff bought on the marketplace can be shared without issue of the launcher or engine rejecting it.
This is the information for publishing to the marketplace: Publisher Portal
But I don’t think they’re accepting C++ based plugins yet, just blueprint. So you might have to look at something like Sellfy for the time being.
It sounds like you could use this to have events in the game trigger based on chat commands, correct?