It sounds like all Chef code will be open source (I'm curious what isn't open source today), but there is no release engineering work in public, and so if you want a supported / stable release, you need to either pay them, make a release internally yourself, or hope that someone like a Linux distro builds a release for you. It's intentionally patterned on the Red Hat model, and very much unlike the MongoDB / Redis Labs / Elastic approaches.

I'm of the opinion that depending on someone else's release of OSS is an antipattern anyway because if you're not going through your own release process, you're not confident that a one-line bug-fix is actually only changing that one line. (The exception is when you know their release is through some decently hermetic build environment like distro packaging or Travis or Docker, such that you expect to be able to replicate that build environment for yourself when the time comes.) But I think a lot of companies use vendor binaries even when the vendor source is open source, so this seems likely to make Chef pick up a few support contracts.