The Mana project was split off from the TMW project back in 2009, with the goal of continuing development of the client and server software, which were until then developed as part of The Mana World. In doing so it enables other games to be based on the same platform.
Some links:
Main website: https://www.manasource.org/
Git repositories: https://gitlab.com/manasource and https://git.themanaworld.org/mana
Documentation: https://doc.manasource.org/
As of today the latest Mana client can be used to play The Mana World. However, the focus of development lies around the Mana server. The hope is to eventually start a project to port The Mana World over from tmwAthena to the Mana server. Meanwhile, there are also other projects using this server like Source of Tales.
This forum exists here as a convenient way for contributors to the Mana project to communicate, as well as for contributors to The Mana World to participate in the discussions.