Here's how I understand it:
* If Pierce plays in 40 or fewer games this year, the deal is completely non-guaranteed;
* If Pierce plays in 41 games or more, the deal is guaranteed for $5 million;
* If the Celtics don't elect to waive Pierce by July 1, 2013, his deal becomes fully guaranteed.
I'm not aware of Pierce having an opt out, and the sites I trust most don't say that he has one, although some sites have reported that he can opt out.