The state, process, or condition of being or becoming out of date
If you search for "mutt" on GitHub, Bitbucket, etc. you will find >700 repositories. There are a lot of people who thought that Mutt needed something extra.
Most of the repos contain the same features, e.g. Sidebar, Index Color. Unfortunately, each repo was created at a different time with a different version of the patch and occasionally different bug fixes.
Searching and categorising these repos took a lot of time. It means that when a NeoMutt release is made, we can categorically say: "This is the only version you'll need".
Alternatively, "This NeoMutt version obsoletes this list of versions".