There are many open source projects whose only reliable, publicly accessible archive is and has been Gmane (due to changes in mailing list providers over the years or loss of their own backups/server resources/et al). If Gmane were to shutdown that would have huge implications for the "institutional knowledge" of some rather long-lived projects.

Personally, I know I've relied on Gmane many times to help solve problems I've had with one open source project or another.

I hope that this resolves well in favor of the protection of this archive as a resource, and I am sad at the recent troubles it has seen.