I found the .dll that held the class I needed, and regasm'ed it. I tracked down its CLSID in my registry, just to make sure that everything took and that the library names were still the same.
I've been using this class successfully inside Visual Basic, but the Committee Upstairs has decided that instead of a nicely packaged .EXE, they want a web app that runs inside this browser of theirs (I guess to justify wasting all that money on a license for it).
use a reflector (i.e.. ilspy) a) given it's not obfuscated
decompile the library