What emulators are allowed?

I know Visual Boy Advance is banned (pretty sure) but I think most others should be ok. I would google it tbh.

BGB and Gambatte. Stay away from the rest, esp. from VBA and all its derivates.

Just as Oh_DeeR said: stick with BGB or Gambattle and you're safe. Bizhawk could be a solution for Linux users as well, but I don't recommend it tbh.