Quick summary ... Yellow Dog Linux was a PowerPC-based Linux and many users ran it on PowerPC-based Macs. Then Apple switched to Intel x86 CPUs so the supply of mainstream computers to run it on dried up.
Then Sony decided to allow "OtherOS" installs on its Playstation 3 and YDL supported that, leading to a lot of new users on this forum - many completely new to Linux. Then Sony decided to remove that feature from the PS3 in a firmware update (version 3.21) and users had the choice of keeping OtherOS (YDL in this case) and losing PSN access, access to newer games, etc. or updating their consoles and losing OtherOS.
Naturally most users wanted to continue using their consoles for their primary purpose -- gaming -- and went with the firmware update.
So again YDL was left without any new mainstream PowerPC hardware to run on.
With the decline in traffic from regular users and the ever-present threat of spammers creating accounts and posting ads and junk, I decided it would be best to have all new user posts go into a moderation queue before they would appear on the forum. In practice, this virtually eliminates spam on the forum but legitimate posts are delayed until one of the admins or mods approves the post. After a few approved posts new users can post without moderation. The only active admins are Paul ("ppietro") and I, and sometimes it may be a couple of days before approval (or longer).
"Back in the day" we checked the forum several times a day we had a good base of regulars that answered questions and helped out, but those days are, sadly, over.
As far as I know, Yellow Dog continues to be developed, but not for hardware that most of us can get our hands on:
http://www.fixstars.com/en/products/7r2/ydl7/