Due to the wild-west nature of crates.io, we can't own a "bevy" namespace that we fully control. This means that certain crate names that we have a high likelihood of using in the future could be claimed by malicious or uniformed actors.
The crate has no functionality yet, they are just so we can stake our claim to the "high value" Bevy crate names.
If you are working on a Bevy-related crate and would like one of these names, please reach out to us! Generally claiming one of these crates for your project would mean integrating your project into the Bevy Engine GitHub organization, but this is not a hard and fast rule.
If you are planning on building a Bevy crate that you would like to be "official" in the future, but you haven't started yet, reach out to us (via the issue tracker or on Discord) and we will claim the name.
I'll go on the record and say that I really think crates.io should support namespacing. This is a real problem and the solution used here is incomplete, toilsome, and dirty.