I wish I knew myself better.
Maintenance and taking the product forward will naturally become part of my job, so that's a given (and I'm happy about it).
What can I ask more for is what I'm trying to figure out and having a hard time.
I'm generally creative with software and products but I'm really bad when it comes to negotiations and figuring out a good barter.
I absolutely don't want to take the legal route and want to work something out mutually.
It doesn't cost them anything, and in the future if you leave it's surprisingly useful if that is a direction you want to go.
I know you are getting a lot of advice saying "get a lawyer". That's up to you.
> I absolutely don't want to take the legal route and want to work something out mutually.
You know, a good lawyer is both good at listening to his client’s goals and good at negotiating. Such a lawyer would avoid a “scorched earth” outcome, if that’s what you want, and also negotiate a better deal than you could on your own. Lawyers who specialize in business transactions are sometimes called transactional lawyers (as opposed to litigators, who specialize in asserting claims in court).
If you are in Canada I can recommend someone who is good, former software engineer and does IP law.
Most of the responses here concentrate on trying to get some kind of financial return for your work.
That's important, but for you it might not be the most important thing (you were giving it away and working on it in your spare time, right?)
Consider asking to make it your full time job, or something like that. You clearly know the field well, and you've managed to build community. Having the company resources behind you and the responsibility to run the project like you want might be an outcome that interests you.