It's "open" in the sense of it was built on open protocols, rather than proprietary ones. Replacing those open protocols with proprietary ones makes you less open.

Google moving from Reader (RSS/Atom) to Current (unspecified protocols) is less open.

Google moving Calendar from CalDAV to their proprietary Calendar API is less open.

Google potentially moving Talk from XMPP to an unspecified proprietary protocol is less open.

Etc.