As mentioned elsewhere in here, this is a misrepresentation of the issue. The problem is that crates.io is a free, volunteer-run project with zero full-time employees who could be tasked with the drudgery of intervening in naming disputes or managing an identity layer. This is unlike GitHub and unlike "Java" (by which you probably mean Maven Central, which is operated by Sonatype). Solve the funding issue first, and then you can start solving the rest.
What do these have to do with the issue of namespaces?
Having namespaces would lessen naming disputes since users would be able to name their crate whatever. Any system will have disputes, so I'm not sure what the argument is here.
I understand why crates uses github for identity management, but it's not ideal that people are locked into using one specific git platform. Github is already an unavoidable entity, much like facebook, but this is a bit of a harder issue to solve without a lot more resources.
That's why there are proposals that delegate the naming to outside systems with their own established dispute resolution rules.
This is due to the crates team requirement of "namespaces are not allowed to create additional work for the team".
So any proposal that makes them the naming authority is out from the get-go.
Sell namespaces? Or verified namespaces I guess? Checkmark and all.