Everything is compatibile Mark! Remember that, all it takes is a skilled programmer that knows what he's doing by creating the script to move the "valuable" information to here in the new forums. Which I would HIGHLY suggest. :)
You can port M$SQL to MySQL and with a bit of minor tuning, it'll work just fine, I have ported a HUGE forums from M$SQL to MySQL not too long ago, and it's doing just fine: adsforfreeforum.com
Now porting it over may take time, and if you have the M$SQL DB you should be able to do it. Just create a new Forum area on here call it OLD WA Forums and insert away, not sure if you can check with vBulletin's docs to see if this will help: impex
Once you have it all over here, I bet you everyone and their family member's will be content. Anyhow guys, keep up the great work! I am loving the main WA site, I keep coming back to see it every now and then or check for updates and upgrades. :)