Geekola

If they were paying you to design something for them and you included an algorithm in what you designed or built. It would become theirs because they were paying you for your expertise. The algorithm is part of that expertise. My belief is that it would now be theirs.

If Ferrari hired engineers to design tires that don't wear at high speeds. Ferrari own it, they paid for their expertise. Their contracts would ensure that and I would assume that it would stand up in court without a contract.

My point in an earlier post, is that people like me would not pay people like you for your knowledge and expertise if we already "owned" that knowledge and expertise. Therefore, we buy it from you, we do not rent it from you. All rights are ours. Action scripts, algorithms, code, the lot.

In the real world, "because most of us are not ferrari." You would retain the knowledge to use such algorithms, scripts code etc. again in other projects that you are commissioned to do.

You are not the only expert involved in the partnership. The guy you build all of this for and, who pays you lots of money, will have put just as much, if not more, sweat, blood and tears into the project as you. "Research, Marketing, Selling, Revenue etc. If the "partnership" dissolves, for whatever reason, and you decide that he doesn't get the .fla source file. It puts him out of business. That cannot be right.