OLSR.org has two major projects and a minor one.
The OLSR.org project started with taking over the development and maintenance of the olsrd routing daemon written by Andreas Tonnesen and Thomas Lopatic. The software has been worked on by a changing team of developers since 2004.
olsrd implements the IETF RFC 3626: Optimized Link State Routing Protocol.
It is considered to be in maintenance mode since the end of 2014, don't expect new major features.
olsrd has its own page on the wiki.
The goal of olsrd2 was to implement the new version of olsr standardized by the IETF. It is a complete rewrite of the codebase of olsrd which ended in the OLSR.org Network Framework. The framework allows the new codebase to be used by different projects more easily than the mostly monolithic code of olsrd.
olsrd2 implements the IETF RFC 6130: Neighborhood Discovery Protocol (NHDP) and RFC 7181: Optimized Link State Routing Protocol v2.
olsrd2 has its own page on the wiki.
DLEP is implemented by a set of two plugins for the OLSR.org Network Framework.
They implement the IETF Dynamic Link Exchange Protocol (DLEP) Draft 17.
DLEP has its own page on the wiki.