I still have an instance of it running and get email reminders about birthdays, but no, I don't think it has been actively developed for years.

TIL: https://www.monicahq.com/ and https://github.com/monicahq/monica

Last commit was a little over 11 months. There do seem to be a couple of signifiant security issues opened since then, with no response. Someone created a fork: https://github.com/brycehans/monica