Ask HN: Should I kill my open source project for a 5 figure sum?

The short version: late last year I open sourced the code I use for creating real estate websites and now a company is offering me $10,000 to effectively kill it. How do I calculate if its a good offer or not? The longer version: These guys got in touch with me a month ago saying that they wanted to work with me on the project but strongly suggested that I make it closed source. I make it quite clear that I wanted to keep it open. We've exchanged a few friendly emails since then and last week they sent me an email offering to pay me $10,000 to close down the project on github and pass ownership of the code to them. I think they made this offer primarily because they realised I was working on MLS / RETS integration and I was going to make that part open source as well. One of the conditions they have made is that I do not compete against them in the MLS / RETS integration space. Its all a bit baffling to me and I don't think I'm going to accept it but just thought I might as well share here to hear what people think. I haven't really got a good way of calculating the value of my project but my gut instinct tells me that in the longer term (3 years +) I will be able to figure out a way to make some money out of it.