Prosody modules do not have releases, therefore the 9999 make sense. However, I prefer to have a released version of net-im/prosody itself. Currently prosody-modules is forcing the development version of prosody. Afaik, the modules are compatible with a prosody relase. In fact, I use some of the modules together with the stable prosody release. So please change the dependency from ~net-im/prosody-${PV} to net-im/prosody. Reproducible: Always I'm meaning this overlay: https://gitweb.gentoo.org/proj/lua.git/
This overlay is dead.