FusionForge is the name of a new project starting from GForge (versions 4.x). It aims at keeping the open-source codebase alive, and bringing contributors of enhancements together.
If you want to install FusionForge, have a look at Installing. To get help on administrating or using FusionForge, have a look at the FusionForge manual of the version you are running at the documentation tab.
For more info you can chat to the FusionForge developers on IRC at
irc.freenode.net on the channel
#fusionforge, or using an IRC web client.
- Developer doc