May I ask what missing fields you are referring to? Why @online/@software/@dataset type in biblatex [1] cannot do the job?

That being said, I think GitHub should acknowledge that it is common for authors to want people cite their paper (or multiple papers) rather than simply the source code. Because this is what counts to the citation in academic. At the same time, there is no reason to not support bibtex/biblatex in addition to the cff.

[1]: See section 2.1.1 in http://mirrors.ibiblio.org/CTAN/macros/latex/contrib/biblate...