The Memory Management Reference is a resource with a very long history, but has not had many updates. In the early 2000s it became part of the MPS source tree and included in the manual. The site www.memorymanagement.org is generated from there by automation at Ravenbrook (see also #165 ).
At one point we had an idea to make it into a wiki using something like MediaWiki to make improvements and updates easy. That could still work. There would be a lot of effort involved though.
A simpler step might be to use a Git-based wiki.