It will mean the death of Maven Central, about which I have mixed feelings. On the one hand, Sonatype deserves enormous thanks for what they have done for the open source world, as does mvnrepository.org. Their central repository has been free and maintained for a long time. Thank you, Sonatype.
On the other hand, it took me three days to release a new version of one of my artifacts the other day. The process for doing a Maven deploy is very complex. It took hours to get my private key to work because the key registries were slow. Then the staging server was slow, and kept timing out. Support was responsive, and said they were dealing with a DDOS attack. On top of that, it takes a while for artifacts to show up in the registry even after they have been uploaded. I'm glad that getting that artifact out wasn't an emergency.
This new Github service separates the registry from the artifact storage, which is the right way to do it. The registry should be quick to update because it's only a pointer. The artifact storage will be under my control. Credentials and security should be easier to deal with. I really hope this works out.