From what I can see in the thread (and I'm not very familiar with the tech so I'm working off of inference here) it looks like the library fetching tool is well equipped to fetch the freshest branch from his repository directly. His responses are very minimal but it sounds like he's objecting to older versions of his library being bundled in and causing breakages on the client side - forking would potentially just make this problem worse from his point of view if his primary concern is the fact that users get out of date code - compared to the concern of code maintenance.

Daniel Stenberg creator of cURL has famously gotten a lot of weird support requests and emails over the years due to his license being shipped with an insane number of different utilities. He has handled them gracefully and with good humor from what I've seen, but not everyone is comfortable with fielding questions from random non-technical users - if that's where this dev is coming from then forking the project would probably let him dodge a lot of the responsibility. I just can't clearly tell due to how terse[1] his replies are.

1. I would say succinct here due to the fact that it lacks the negative connotations of terse, but it also implies a completeness of information which sadly isn't here. Please don't read terse as insulting or negative in any way.