I'm currently working on a "trade robot", too. My primary aim is to make profit by having the code trade for myself, but I want to commercialise the project later and do what OP does. So, do you think that there is way of offering such a service without taking their API keys? Sorry, but I cannot give my precious source code.
Ok I won't even begin to try to explain to you the legal liabilities inherent in writing a trading bot and selling it. It should be obvious that you will end up in a huge tank of hotwater if you make even a tiny little mistake. Don't believe me? Go find my ATP thread where we discovered a week into trading that although everything looked good when the market was moving a slight oversight (dividing a float into an int) was actually costing people money. I'm really, really lucky I (as Isis) had the support of a community who were willing to take a loss to test a bot. Still people were pissed and I won't lie there were some nastygrams (nicely worded nastygrams, but nastygrams nonetheless).
If bitcoin had been a real currency at that time (I think it was worth < $10), I highly doubt I would be here explaining the lesson I learned to you.
Still that was the best way to develop it. Open source it, release it to the community. Test your algorithms on yourself. If you don't have the funds to test it on yourself then find a business partner who is willing to take the risk and thus reap the reward. Use their funds. Not ours, thanks!
I'm very proud of the fact that even though I haven't touched my ATP bot in 2 years that a whole community has grown around it and taken it places I never imagined.
That was only possible because I opened the source from the beginning.
Point of fact, this is not an easy business to be in. If you don't have at least some skill as a programmer, mathematician and day trader in your own right, you're going to take massive losses.
I've programmed trading systems for the likes of JP Morgan and I still make occasional mistakes that nearly wipe me out.
There's always something going on you didn't forsee.
I applaud you for trying, but please until you have real experience or feel you have something innovative to contribute, play with your own money.
If you truly think you've innovated something, then share the code with the community. No one is going to steal your super secret codez. Very few people would even know how to compile and run it, but they can probably help you vet your algorithms by explaining things you never considered. But that's only possible if you share them.