I don't understand the paranoia, and how open source fixes this.

At any rate, there are a few people linux multi-boxing wow on the forums, they are using sendEvent tools last I looked. Essentially hotkeynet for keyevents only, without toggle. However you could have a target window which was used for itself sending keyevents which would then roundrobin or what not.

I believe you could find someone on the forums that would be able to give you a good deal on a hardware multiplexer.