What is the source of your data? How do you define "government activity on GitHub"? Do you look at domain used in contact, affiliation, etc.?
Querying wikidata may also be useful https://github.com/github/government.github.com/issues/877
Added: note about your project at https://github.com/github/government.github.com/issues/1167
The goal is to have a deeper level view of public government orgs, including a more granular view of contributors and how they interact with code.
Great idea about wikidata! That's another data rabbit-hole to climb down into.