To the extent possible under law, the XMPP Standards Foundation (XSF)
has waived all copyright and related or neighboring rights to XSF's
bibliographic data.

That is, the bibliographic data, which is also accessible via
https://xmpp.org/extensions/refs/, is put in the public domain via
CC0 1.0 [1].

1: https://creativecommons.org/publicdomain/zero/1.0/