People familiar with the transaction say Google’s plan is to leave Invite running as a stand-alone unit, which will work at arm’s length with exchange’s like Google’s AdX as well as competitors like OpenX, Yahoo’s Right Media (YHOO) and Microsoft’s AdECN (MSFT).

That makes sense, because ad buyers who use Invite, like Publicis’ Vivaki, expect to be able to buy inventory from multiple exchanges.

But over time Google does plan on investing in Invite and integrating it into DoubleClick for Advertisers, its ad serving technology. Invite users wouldn’t be required to use DFA, but the two would be designed to match up seamlessly, sources said.