That's what director of intelligence John Negroponte (left, from Wikipedia) calls his new operation at CIA headquarters in Langley, the Open Source Center.
What he means in this case is making better use of information that's already on the public record. It's upgrading an existing operation called the Foreign Broadcast Information Service, designed to monitor press reports in other countries.
As with many corporations, open source in this case is just a cute name for doing what should have been done already, making use of what people are actually telling you before trying to ferret out what they may be thinking. In many cases they're the same thing.
It would be nice if The Agency were making better use of open source tools in all its work, but if they were they wouldn't say, and I wouldn't want them to. Still, it's nice when they give a shout out to you as a buzzword.