zlacker

Agreed. I think most people think an open source project means there is also a public repository, a public issue/bug tracker which is generally open for anyone to participate, responsive developers handling those issues in a respectful and "professional" manner, and as mentioned, pre-compiled builds for the three main OS families, and likely more specialized builds as well.

I'm sure there's more I'm missing; these are the first I came up with. Do people expect good documentation these days? A Discord server or other chat forum?

>>eesmit+(OP)
I think you're right, but a lot of these things are dependent on how large of a project it is. The highest order bit is some sort of open, democratic-ish (at least nominally) governance and/or acceptance of patches from outside of the team, I think. It starts with "public issue tracker and responsive, professional developers" and then grows from there.