AI gets it pretty close to working. Close enough that I can hire a dev to clean it up and get it going.

This simply just isn't how that works. 95% working can very, very easily be 100% shit. Because of the lack of professional guidance and structure, the last 5% could be very difficult or impossible without a complete restructure and rewrite or the whole code base.

This has been true since outsourcing code become popular. So many times I've been asked to "just finish the last 5%" just to have to explain that the last 5% is actually 150% the amount of work (now I have to untangle this mess).

At the moment, that project is not covered by the open source license since the original code is gone

That's not how most open source licenses work. Which is really the crux of the issue. If the new code was based on the open source code in any way it is now open source (at least for GPL code).

If you took a popular open source project, looked at the code and rewrote it by hand, the resulting code is open source. Even if you wrote it in a totally new programming language. I don't see how AI reading and reproducing the code is much different in this sense.