Rule #1 Cover your arse - take note of what people say here but these issues are obstacles to overcome and if you work out the right strategy backed up by the right advice then things can play nice and life is great... otherwise you'll get fked. So work out how not to get fked and know what you can/can't do from a legal, financial and karma perspective etc. then find the way to cover yourself and move forwards.
Rule #2 It's a lovely world we live in, all this openness, though it means competition is rife - don't be fooled into sharing a great idea and losing it, goes back to #1 about covering your arse
Rule #3 It's best to remember the adage (a) bullshit walks and money talks... don't faff around thinking about doing this - JFDI - i.e. go build that prototype in your bedroom that you can tear up/down to demo on an Amazon EC2 image with Mulesource middleware (for example it's easy to get a great demo running in the cloud that only costs you for the time it runs!) and prove this can be done because until you've actually got something to show, discuss and demonstrate it's a load of hot air or should I say vapour-ware. Adage (b) rings similar i.e. "the proof is in the pudding" so get baking and then re-visit the whole legal thing because....
Rule #4 Ethics and co-opetition: you are in a weak position until you are able to influence the game i.e. people will benefit more with you than without you - so this also takes into account the rights/wrongs but before you give away a great opportunity to someone else, especially an employer, work out how to avoid doing that! See #5
Rule #5 Read smart books: Innovator's Solution by Claytensen and Co-opetition by Nalebuff/Brandenburger tell you of real case studies on how the big boys do these deals and what's at stake - sometimes you make more money NOT doing things, now would be the time to learn your real value in this 'game' and you get to realise why game theory is so cool in the process. If you have time also read some Sun Tzu, my favourite.
HTH.