I know among the pfsense group originally there was skepticism that it wasn't back doored by a government agency (not because there was proof), because of the fact it had such a great feature set while being so new a project. Now that it's open sourced, I'm interested to see if people pick it up. It definitely looks legit.
Before SoftEther went open source, it was sold commercially as early as 2004. It was renamed PacketIX VPN around 2005 and is still sold commercially under that product name at https://www.softether.jp/1-product/11-vpn (it's up to v4.0).
I remember reading that there was a 10-year agreement that finally ended at the start of 2014, allowing the original developer to go open source. The source tree is different from PacketIX's though, so some of the features are still not available yet in the open source version.
