These are the current known maintainers of Dia in various distributions.
They should be contacted when new releases (and candidates) come out.

Debian: Debian Dia Maintainer <dia@packages.debian.org>
NetBSD: Martin J. Laubach <mjl@netbsd.org>
OpenBSD: Margarida Sequeria <margarida@openbsd.org>
FreeBSD: gnome@freebsd.org
Mandrake: fcrozat@mandrakesoft.com
PLD: kloczek@pld.org.pl
SUSE: Mads Martin Jorgensen <mmj@suse.de>
RedHat: alexl@redhat.com