The LANforge SIP call generator utilizes the VOCAL SIP stacks and soft-phone programs. Candela re-wrote much of VOCAL to remove threads and otherwise make it more stable. In doing so, all features not related to a soft-phone were removed, so it is no longer a soft-switch like the original Vovida VOCAL project was. It is a good programmable soft-phone, however.
Candela Technologies currently hosts
a git repository for vocal2:
git clone git://dmz2.candelatech.com/vocal
To build the code:
cd vocal ./configure --with-shared-libs make