Hi. I don’t have (server-side) access to that forum so can’t really help. I notice the Tinderbox wiki is also now offline. I suggest email to Eastgate (firstname.lastname@example.org) to inquire about the status of the old forum - . When last active, it was running but locked, i.e. read-only and no posting.
At some point it does make sense these forums are taken down as otherwise they spawn a steady stream of posts about now-fixed issues (or missing-now-added features). Despite this, there are interesting posts about things like obscure cross-app data migration. On a more general note, saving the latter and removing the dross of the former is a systematic problem for knowledge resources on the Web which now tend to rely on the ‘tyranny of search’ (if you can’t guess the search term you likely won’t find it!) to find old things rather than expend effort on some human curation. I say this from the experience of having moderated forums and run FAQs, etc, since the '90s and am not suggesting the problem is easy to fix