Likestofly
I think you have answered the question in your post. As the RAF Sports Parachuting Club it cannot make money - just like a Mess bar it has to be not for profit. It also has to run under a GAI with a Gp Capt or above as the Chairman. So if it was set up as a going concern, making £500k of profit over 5 years without investing that profit back into RAF Sports Parachuting for the Serviceman then it would be in breach of the arrangement for an encroachment on Crown Property.
However, it could pay the 'going rate' with MOD Wider Markets and make all the profit it liked. But that is not in the spirit of how Service Sports Associations are run and how best value is offered to Servicemen of any rank.
Finally, you mention JSAT. If there was any mixing of Public and Non-Public monies (not that I know that there was or was not) then that is an easy way to be "expelled" from any agreement to use Crown Property. A lot of the JSAT organisations have to be exceptionally careful of this.
Maybe the Army have been a bit more cognisant of these things?
LJ