It sounds like 3 is for charities and 6 is for business organizations like a chamber of commerce. The former has tax-deductible donations and can’t participate in lobbying or political campaigns. It seems like 6 would have been a weird choice here.
Not so weird, the Rust Foundation is a 501(c)(6) after all, like the .NET Foundation or the Eclipse Foundation, but from all I know about Bevy and the people behind it a 501(c)(3) suits it much better.
