It's similar in that it's peer-to-peer, but doesn't require an auth/directory server to establish connections. If any known peer is accessible, the two can authenticate directly.
NAT traversal is an implementation thing, and I favor Jabber as the out-of-band these days since everyone can get at least a GTalk account.
Though we now have libjingle, which basically merges both of these things and would probably elegantly solve the problem. But p2p vpn's aren't much use if you have to control the NAT router you're attached to.
Isn't that deprecated in favour of Google Hangouts?
p2pvpn <http://www.p2pvpn.org/> uses BitTorrent trackers for it - which is actually a pretty good solution, but sadly also - no NAT holepunching or even UPnP yet.
Though I have been trying to find a VPN which uses a Tor hidden service to define network rendeavous point - since Tor is distributed and available, you could issue invites with the hidden service ID, and then send real IPs to members to establish P2P (so, not using the anonymity, just using it to bootstrap the network). SocialVPN does something similar, but I couldn't get it work reliably in tests (it would go up...then my hosts went down and I couldn't get them to appear to each other again).