Hi,
Skype never played with iChat.
It never played with anything else either.
AIM can relay Video chats through it server and iChat/Messages can be set up to do this (Later versions of iChat).
Other than the Name/IDs nothing is centralised about Skype.
Last time I ran it was in Leopard.
I was using Little Snitch at the time (still do)
iChat/Messages makes about 3 or 4 Logins connections per Account. (Buddy list, Buddy Pics, Profile etc)
It then uses 4 more port connections to do an AV chat.
Skype seems to make endless connections (I quit about the 40 mark, Decfom in iChat reported over 100)
These seem to be "sharing" end user bandwidth to spread the load for the video or Audio chat.
I don't know if it still does but the Skype Preferences used to list that download's Port number
If you did not open this in the firewall or router then it would default to port 80 or 443 (Always Open ports) circumventing your firewall or Router settings.
Apparently the port used to vary from Download/install to Download/Install.
See this site for the instructions to Look up the port before Forwarding ports on the router model.

10:17 PM Wednesday; February 13, 2013
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