From the README.md file:
If you’re using a VPN service today, you may have found the following limitations:
1) All or nothing. Either ALL traffic goes down the VPN or none – unable to be selective.
2) Only one VPN at a time. Cannot selectively route certain sites down one VPN, and others down another VPN.
3) Unless you’ve configured your VPN at the router level, it’s likely that only a single device can use your VPN at one time.
This project serves to address each of the above – see the FEATURES section.
Please review my blog post here http://darranboyd.wordpress.com/2013/07/05/selective-vpn-routing-solution-dsvr/
Note that this software runs on a Raspberry Pi. Full text and download links:
DSVR (Domain-Specific VPN Router) (GitHub)
If for some reason you don’t want to run this on a Raspberry Pi, but would instead prefer to do something similar using a DD-WRT based router, the same author covered that topic a couple of years ago:
StrongVPN PPTP on DD-WRT – Source based routing (improved) (Darran Boyd)