The last update is Jul 15, 2018:
https://github.com/jmapio/jmap-perl/commits/master

Spec has changed quite a bit since then:
https://github.com/jmapio/jmap/commits/master

I am hoping to use along with https://github.com/virtualmin/virtualmin-gpl (also in Perl) which uses Dovecot: https://doxfer.webmin.com/Webmin/Dovecot_IMAP/POP3_Server

Thanks!

Marc