If you write it yourself or contribute the algorithms to the programmer, it's a white box. If you buy someone else's system, without explanation of the algorithms, it's a black box (and you've probably been taken).
I'm a programmer and a trader. If someone wants to contribute a winning trading algorithm (that I'm not already working on), I'll be glad to write/implement a system to trade it in exchange for being able to use it, as long as the relevant markets are liquid enough to support both of us, and you don't want to sell it to anyone else afterwards.