Selling program as investment?

I've got an algo program I've been working on for about 3 years, it's been testing real & historical data and although its not 100% bullet proof, it can trade almost any time frame and any FOREX pair and make money. There are situational thing that may occur that can cause it to loose money, but it's few and far between.

I have a friend who is willing to give me money to start an account, but all trading is not without risk, I can't predict the future!

I wouldn't even consider selling it in it's current state, it's a bit clunky but works and would need more refining to be sold to the general public, but he has seen it working and knows of my many conversations how it is going. Need money to make money and if all the figures hold up then I can use some money it is making to further refine the program.

I want to draft up some legalities or terms of agreement that protects myself from having to repay him if the absolute worst case scenario occurs and it looses the entire amount. And some terms around halving the profit each year and payments required to support it running.

I don't want to rip him off he is a good mate, and I don't want expensive lawyers involved or anything like that. Basically I've been running test account data in real time and historically against it and it has been proving successful. Is there anyone that can help me come up with a few terms that we can both sign to agree to protect myself from not having to pay back the money if it goes catastrophically wrong?

And does anyone know if what I'm doing can get me into trouble, by that I mean like. I can't get charged for taking money from a friend if it looses it or something like that can I?