The accepted answer is a bit stale and some of the links have changed. I'm deep in this particular Hell myself, so this is for those that have to deal with Build Forge and the quirky API and the spotty documentation.
The video has moved. It's now found here:
https://mediacenter.ibm.com/media/Using+Build+Forge+adaptors/0_9g8f456l/33943992
After you watch the video, there is a cookbook instruction set on how to make a basic adaptor in ClearCase for Build Forge here:
http://www.ibm.com/developerworks/rational/library/continuous-integration-build-forge-clearcase/
I have managed to make a perl cli script that will fire a Build Forge project build, but it doesn't get the tagging correct yet. So far, the best method I've found is to schedule the build job within Build Forge, then the deploy is run separately with a cron job that fires off another perl cli script. I played games with the tagging to smoothly hand it off from the build to the deploy by having the build process write the tag to a file outside of Build Forge where the perl api deploy script picks it up. That is a broken kludge, but it's the best I've got so far. I'm hoping that the adaptor can make that process more precise. I'll update this entry once I have a full solution, but this is the crankiest tool set I have ever had to deal with for Continuous Integration.