Or I am always a fan of putting a checkbox in the project's Settings page "show 'download source code' link" and a text box underneath it with "source code download label", enabling the project to use language they are happy with

That said, I am also cognizant that "checkbox overload" is a real thing, so merely "for your consideration"

We're indeed pretty hesitant to add options for these things, it makes it harder to refactor the UI if you have to account for all settings.

Google Code used to have labels, in particular one named "featured". You can label files in the release with it, and the ui put those at the top. Consequently it was clear to users which release files would be best.

"Source Code" has two meanings. One is the preferred form of contributing to the project. The other is the preferred form for building and installing it on a system. Sometimes they are the same. However I argue someone going to a release page is more interested in the latter, and the former is confusion.

I'd suggest making your UI reflect the page visitor's goals. "Repository Archive" is better wording, but still not that good.