6.x-2.x unsupported?

I've got Zeropoint 6.x-2.5 installed on my site. I'm getting security warnings that my version is unsupported. I don't even see the 6.x-2.x branch listed on the module download page, though I was able to find the release notes for the version, so it obviously exists. What's the deal here - why does this branch exist if not supported, and how can I fix it? Can I safely downgrade to the 6.x-1.x branch? Or can you somehow make the 6.x-2.x branch supported so I'm not getting these warnings? It's obvious that some effort has been put into it, so something doesn't match up here.