IGS08 epoch 2005.00 was introduced in 2011.
It is a global (geocentric) system based on GPS/GNSS only and was designed to be are consistent with ITRF2008 positions. It is not a new datum. It is an epoch (update) of ITRF2008. The ITRF2008 positions of a particular site may differ from its corresponding IGS08 position but their velocities remain identical.
External link to more about IGS08
NOTE: As positioning technology moves towards a global solution, the term GPS is gradually being replaced by Global Navigation Satellite System (GNSS)
For more on this topic see Google GNSS and read on!