In case of single-player game: beta version can be a demo (shor) version of game.
In case of multiplayer game: limit amount of users and wipe instance after release.
Possibly "A non-disclosure agreement (NDA)" that If your testers can sign it.
About Ideas and conceps - Sadly there is no options. The only thing you can do - is finish game and release.
You can host some parts of game (resources or data) on some server. This server can also collect information about running game instances, crashes, and so on. And game simply not working without connection to this server. So when yout test period ends - shutdown your server.
It may save you from most common cases of piracy.