AddictingGames.com was launched in 2002 by Atom Enterainment, Inc (who also owns another gaming website: Shockwave).
The logo was changed on March 25 2005. AddictingClips became a division of the website by 2006 (in which was later changed into AtomUploads). Still used on some games (e.g. Castle Tales)
Six years after Viacom acquired Atom Entertainment in August 2006 for about $200M, the website was changed to "Nickelodeon Addicting Games". The version without the Nickelodeon logo is still used today.