But now there is no official fork of youtube-dl, so development will either stop or be fragmented. And users will not want to trust any given fork, so downloads will taper off.

If the original creator endorses a fork, is he making himself liable? - not sure what happens if you repost after a takedown notice.

And the involvement of the law, and the publicity will lead overall to self-censoring, as most devs won't want to deal with this...

Doesn't seem to me to making things worse for the RIAA