this forum is totally accessible, CSS does not determine whether something isaccessible or not, I can build a fully CSS compliant website but that does not make it accessible.
have you tried searching for speedball ? since it is an external project we do not know what it's status is
SpeedBall 2 (a.k.a.: SB2 or SBII) was last updated to the 3.4.05 code with no security updates. Several attempts have been started at a SpeedBall 3 (a.k.a.: SB3 or SBIII), but none have been finished.
If you really want CSS, you can find the last release of SB2 and apply all of the updates that were made in the 3.4.05 to 3.4.06 update. As far as I know all the updates are fairly well documented and compiled down into a single list.