I guess no one will be refused at the door, but as a rule of thumb we could agree that participants should have something to contribute to the discussion, be it a pressing question they need to address, ideas for collaborations, tips they want to share, or some news on development/design.
I guess games GIG on thursday and shindigs are good for introductions and starting to get involved.
Is that non-inclusive? Would just "open to everyone" be a better approach? is that even an issue outside school circles :)