If you're looking for evidence in the public repo, consider what's not in there: one co-founder is missing, and so are the commits from the other author/co-founder for over a year. Not the signals you want in a dev-tooling project.
Except how many users do they have? If I were a VC fund looking to give them another round, I’d want to know their metrics, whether that’s users, downloads, or revenue. Judging by their blog, it’s been a year since they raised the money. Have they produced anything other than a bunch of code? Because code isn’t worth much without users.