[evook]

I don't recall the exact context anymore but during the Microsoft Build this year it was said by an employee at Github that the service came with the acquisition which is the reason it was and stays C#.

[Kwpolska]

You can also find many leftovers with the "VSS" acronym, like https://github.com/actions/runner/blob/main/src/Sdk/Common/C... or https://github.com/actions/runner/blob/main/src/Sdk/Common/C... - which also mentions TFS (which is yet another acronym that used to refer to the Microsoft team-development thing).