Well it did have to change its name from GAIM to Pidgin at some point because it infringed on "AIM" by AOL. And whether or not Pidgin was fully "TOS-compliant" (which it might have been depending on the service we'd be looking at) is not as relevant as whether these terms would have been actually legally enforceable or not.

That was due to a trademark violation and nothing to do with TOS.

We (Pidgin/Gaim/Finch/libpurple) have never been TOS compliant.