Messages is the App.
It is iChat+ (The plus bit being the iMessages Account that can use an Apple ID with iPhones and iPads).
It can use a GoogleTalk ID.
My Messages Menu > Preferences > Accounts with Buddy lists in the background (including the Gmail one)
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously