well to tell the truth, ive seen alot of contracts that state anything the person developers while under this contract is the property of the employer(BT operate this policy, so also most of the investment banks). i.e. you work for a bank and create an app outside work which turns out to be a million dollar deal, they can technically take it from you.
apparently this exists because they claim they provided you with the skills so you could develop this app. whethers its opengl or direct3d, something which banks dont use. now maybe steph can tell us whether they’re might be a loop hole in relation to them, but i guess they could claim that you learned to develop and tone your c++\c#\java skills while working for them, and had access to books, methodologies etc.