Sonicwall SOHO2 <-- vpn --> open/free bsd

We currently have two or three sonicwalls, but no vpn licenses.  We
would like to get a few vpns set up, but we have a few questions about
the sonicwalls before we drop $$$ on vpn licenses. 

First of all, we are going to move away from the sonicwalls at some
point.  Ideally, we would get the VPN licenses, and as we phase out the
sonicwalls we would use them to connect back to some sort of vpn server
ideally running openbsd or freebsd.  

My question is, how standard is sonicwalls ipsec implementation?  Can
they interoperate with a bsd vpn server? 

tia, 
Dan