Although it would be certainly nice to be able to deploy on Mac and Linux too, the PC/ Windows platform still has a player base second to none - Steam alone has 100 million registered accounts and at least 75 (%) of them are active users.

No matter what the engine/ product says it's not like you can port the game to various platforms with a single click, there's always more stuff to be done, for example have different Windows, Mac and Linux computers for testing. If you haven't managed creating a complete game for the PC alone yet (no offense!) I wouldn't suggest targeting a release on multiple platforms for now.

Btw. I've moved your thread and "I have a stable Gamestudio RPG Template now buggy" sounds a little contradictory to me.