Parchive development has moved GitHub.
PAR2 (libpar2/par2cmdline) continues to see active (if sporadic) maintenance. The most recent tagged release was 2020-02-09 but there've been a handful of PR's merged since. [2]
PAR3 has a reference implementation and alpha spec (libpar3/par3cmdline) which is based around Blake3. [3]
OG PAR (libpar/parcmdline) is legit unmaintained; the last release was 21 years ago. [1]
[2]: https://github.com/Parchive/par2cmdline