The CLA was put in place in December of 2018 [1]. Presumably contributions made before that were under inbound=outbound terms [2], meaning the contributing author licensed their exclusive rights under MPL 2.0, which is a file-based copyleft license. (see the chart at [3]).

[1] https://www.hashicorp.com/blog/introducing-a-cla

[2] https://docs.github.com/en/site-policy/github-terms/github-t...

[3] https://en.wikipedia.org/wiki/License_compatibility#Compatib...