From: http://www.softether.org/

SoftEther VPN ("SoftEther" means "Software Ethernet") is one of the world's most powerful and 
easy-to-use multi-protocol VPN software. It runs on Windows, Linux, Mac, FreeBSD and Solaris.
SoftEther VPN is open source. You can use SoftEther for any personal or commercial use for 
free charge.
SoftEther VPN is an optimum alternative to OpenVPN