It is crazy that some instructors get so upset at guys training elsewhere. However IMO students should be expected to be 100% honest about things. I am certain 'some' of the time instructors are more upset with the dishonesty, and guys being sly (often unnecessarily too).
From day 1 my 2nd degree black belt Brazilian professor has known i am down with 10p and the 10p family. Also that i train around. Although i do 90% of my training with him, and i represent him in competition etc, he understands i have many friends outside of our team (Checkmat) that i like training with too. Plus my instructor still competes and trains at a couple other places in the UK and Brazil as well.
Guess all i am saying is fellow students, honesty is the key. Always be honest with yourself and your instructors. And if being honest with them doesn't work out then most likely your instructor is putting their needs before yours.
To affiliates not allowing their guys to train at other affiliates schools, well i don't know what to say to that. It is fucking insane! :-)
e2a - sorry for going kind of off topic there with my ramblings. :-)