To keep track of latest developments in the OpenSceneGraph we now use Subversion. Note OpenThreads is now part of the OpenSceneGraph so separate checkout is no longer required. Also osgProducer has now moved out of the core OpenSceneGraph project and into its own repository/distribution, this means that the core OpenSceneGraph no longer has any external dependency on either OpenThreads or Producer.
To check out OpenSceneGraph:
svn checkout http://www.openscenegraph.org/svn/osg/OpenSceneGraph/trunk OpenSceneGraph
To check out OpenSceneGraph-Data:
svn checkout http://www.openscenegraph.org/svn/osg/OpenSceneGraph-Data/trunk OpenSceneGraph-Data
osgProducer has now been moved out of the core OpenSceneGraph distribution into its own project, which you find here.