I am a corporate lawyer for startups, and advise on this type of issue frequently. Even though users don't get source code, they are privy to proprietary information, so your concern is legitimate. There are good suggestions in this thread of the types of legal concerns you might have and how to address them. I would suggest that, whatever language you end up using, you can incorporate it into "terms & conditions" and use a "click-wrap" structure to implement it. This is pretty standard "check here if you agree to our terms & conditions" box. It's unibtrusive, and an important part of protecting your company's confidential information and trade secrets. Happy to chat further.