I think some folks have found a way to make 1.2 mods work on a 1.5 build, but we haven't tried this and we don't try to lead people into thinking it is possible. Still, I think others have gotten it to work somehow. We are currently working on finishing the 1.5 port, and then adding a bunch of new stuff to it for our next build (and we really don't have any release date in mind yet), but currently we'll just have to advise using a 1.2 build for installing the mod on.