Winter kindly provided those boards for free for many-many years because they weren't allowed here (or anything that would make it look like official endorsement). It's a reasonable thing to do, I think.
I have very good memories of the SWC development and discussions, thousands of PMs. As well as seeing the secret development board for TLD, that one was a goldmine. You can also see stuff from Yoshiboy and the others, as well as the first mentions of what ended up being OpenBRF.
A good bunch of us noticed, Earendil included. It has been in read-only mode for eight to seven years. Things just change, this will also happen to Discord one day, and no one will be there to archive the discoveries in the public web like we have with any of these sites that will live for years to come inside the Wayback Machine. (Hi there!)