I think the software for this is free but he has proprietary rights on the design used. That doesn't mean you couldn't design your own but USB control is alot more complicated than a serial port control.
An easier version is use DSLR Shutter from
stark labs (a serial port control) & maybe a USB converter cable if you only have USB ports.
I'm doing that at present. I'm using this opto coupler design (although leaving out the focus diode):
http://www.beskeen.com/projects/dslr...ON%20TWEAK.pdf
Here are some other ideas:
http://www.covingtoninnovations.com/...onRelease.html
http://www.jim-easterbrook.me.uk/astro/ap/remote/
Hope this helps.