BDF is a bitmap format, so it can't be [trivially] converted to an outline format. What those converters probably mean is that they embed a BDF into a TT file (something I once did, when making Arasan). But many systems simply ignore those these days...
Now, if your objective is to "reproduce" a bitmap font via outlines* I have some custom software that does that, but I haven't fired it up in years... Feel free to email me: hpapazian thatsymbol gmail dot corn
* Like this: http://www.themicrofoundry.com/manademo/
hhp