Source code of debbugs.gnu.org

[Mekeor Melire]

Hello :)

Which version of Debbugs does debbugs.gnu.org run? Where is its source code? In 
contrast, I could find Debian's Debbugs' source code easily public at: 
https://salsa.debian.org/debbugs-team/debbugs

Also, some pages on debbugs.gnu.org mention text-files like bug-mailserver-refcard.txt and bug-log-mailserver.txt which ought 
to be accessible via HTTP. Unfortunately, I could again only find 
the respective links for Debian, e.g.: 
https://ftp.debian.org/debian/doc/bug-mailserver-refcard.txt

Thanks in advance :)