I've been talking with folks in the OpenOCD IRC, and they've noted that we should be using the ftdi driver, not the old unsupported ft2232 driver that the bus blaster docs recommend.
Also, we made a board configuration for writing to the CPLD. The forum software is convinced I'm a spam bot, so I can't link the file, but I can paste it here:
# Dangerous Prototypes - Bus Blaster
#
# http://dangerousprototypes.com/docs/Bus_Blaster
#
# To reprogram the on-board CPLD do:
# openocd -f board/dp_busblaster_v3.cfg -c "adapter_khz 1000; init; svf <path_to_svf>; shutdown"
#
source [find interface/ftdi/dp_busblaster.cfg]
ftdi_channel 1
jtag newtap xc2c32a tap -expected-id 0x06e1c093 -irlen 8
Put that into the board directory and you're good to go. In a week or so that should be merged into the main branch, so if you're reading this in the future, you may already have it.
This is really great, thank you. We submitted a patch previously and offered free boards (open hardware to go with open software) but there wasn't any interest. The offer still stands if any OpenOCD contributors want free hardware.