According to the http://purple.worldforge.org/cvs/forge/clients/ list, Apogee is a client for worldforge.
The document http://purple.worldforge.org/cvs/forge/clients/apogee/README says:
This is apogee, an experimental codebase to trying and testing 3D client ideas for worldforge. It currently consists of a single codebase which builds two executables, apogee and perigee. apogee renders its view in the isometric projection, and perigee render in the perspective projection.
In order to build apogee and perigee you will need cal3d 0.6 installed with headers on the include path in a directory called cal3d, and libraries on the link path. You will also need the demeter terrain engine from http://www.terrainengine.com/ installed, with the headers on the include path, and the non OSG version of the library on the link path.