Well, I cannot really give you a good answer, because I just don't know it. But if you have the answer, would you let me know it?
But I can tell you, what I did so far: I released my trade API implementations as opensource and now I have some people using them in their apps. That helped to find some bugs.
I did not release any trading strategies to the public, although I gave the sources to a dozen interested developers.
What I have built is a application on top of al the trading APIs and found it rather uncomfortable to release all the code to the public, but I think I will do it anyway. Distrusting comments from cummity members worry me more that releasing the source code. As for the business model I will take the feature voting with BTC option. This way I probably can make a few BTC off my time invested in a non invasive way. I'm really looking forward to release it to the community and getting feedback, because it's the first application I really finished personally in quite a few years (allthough being a software developer most of my life now).
Mt. Gox source code is already open. Why dont u modify it a little and re-implement it ? ....just a thought
I'm not looking to create the next exchange, I'm building an application on top of all the exchanges.