Not just EFF/ISRG could fork it, anyone can. To be precise, I've forked the code too! I just didn't rename it to my own version or something like that. And for the why: no commercial "smudge" and restore Let's Encrypt as the default ACME API could be reasons.
But to be frankly, any discussion about acme.sh including forking it is offtopic in this thread about certbot & snap IMHO 