Csound b3-emulation patches are mentioned there,
and azr3-jack[2]. I don't know how well azr3-jack suits
for a Hammond emulation but it makes nice sounds.
At least it's a GPL option for not starting to code from
scratch.
A tool that I use sometime is directhammond v2[1] , for csound
[1]
http://www.csounds.com/jmc/Instruments/instruments.htm
--
cb