It might make more sense to outsell them. Advertise your library as being used in a successful commercial product yet better supported by the original developer which is you.

This idea that you own intellectual property is questionable. If someone hears your story or song or sees a picture you drew or downloads some source code then that has escaped into the wild and is no longer controlled. Given how much effort leads nowhere at all it is a kind of gift to be valued in this way.

Instead of trying to own things that are conceptual and cannot be owned it makes more sense to control release and advancement. Get people to pay up before any source code can be downloaded, and once the designs or code or whatever is out there then offer more and better to the highest and best bidders.