It's different from a VPN because it includes a notion of identity (you don't just know I'm on the corporate network, you know I'm asdfhero). It is very similar to Google's BeyondCorp strategy though.

Given that the team are Xooglers, that's presumably not a coincidence.

VPNs also have a notion of identity. You don't join the network just because you know the IP address of the VPN server.

apenwarr is the author of sshuttle; so that might give you some background