The 04 version includes fixed up models of the pipe hybrid, shotgun hybrid, and midwife (modifications done by RocketMan). They all now have proper joints - as result, their necks are no longer rigid (headtracking will work), and the midwife and shotgun hybrid will now launch their projectiles properly with their right arm (and not the abdomen). A few small model flaws have been corrected as well. Also, a previously unused corpse model with a ripped off arm is now used at a couple of places (corresponding ripped off arm model created by Olfred). This update makes sure the Rebirth mod will be fully compatible with the upcoming Community Patch release.
For proper mod installation/activation, check the Mod Guide.