The official firmware uses the Bliss menu (which Bliss is no longer developing).
AKAIO is a different menu which has all of the features of Bliss and then some. AKAIO is being actively developed by Smiths and Normmatt, and runs on both the AK2 and the AKRPG (which is why it's named AIO -- All in One).
Gelu also has his own menu for the RPG only. Gelu's changes to his menu are usually incorporated into AKAIO.
-Bri