It's a single C++ file containing some matching rules to identify tor users. From the article it's not very clear where they got the source from and if they have the rest of the program (although they show some other screenshots).
It would be interesting to see where the data is transmitted to from the monitoring nodes.
It certainly is not a c++ file, but it does include a very small portion that seems to be c++, and it does not look like any language I've ever seen.
It is probably a DSL.
e:
"""XKeyscore provides a modular architecture in which tens of thousands of small computer programs, or rules, written in XKeyscore's specialized programming languages called Genesis and XKScript as well as general-purpose languages such as C++ and Python,"""
It would be interesting to see where the data is transmitted to from the monitoring nodes.