Generally the BiDi code allows both kinds of languanges to be displayed properly on the same page. This is a pretty cool feature if you speak these languages, which a lot of people do. The holdup is that it is awaiting a lot of reviewing, because BiDi is a large set of complex changes to many areas of Mozilla. MathML has already been turned on on the tinderbox builds. A company called Design Science owns some suitable fonts that they're willing to contribute.
Negotiations are in progress, with a few loose ends to tie up.
Bradley Baetz has contributed gopher protocol support. It's the same level of support as Netscape 4. Along the way they fixed bugs along the way that were plaguing the trunk builds. Nice one, dougt. Still a bit buggy.