OpenConnect GUI is described as 'is the graphical client of OpenConnect for Microsoft Windows systems (or any other system Qt and OpenConnect run on)' and is an app in the Security & Privacy category. There are six alternatives to OpenConnect GUI for a variety of platforms, including Linux, Android, Mac, Windows and iPhone. The best alternative is Tunnelblick, which is both free and Open Source. Other great apps like OpenConnect GUI are sshuttle (Free, Open Source), OpenConnect (Free, Open Source), Cisco AnyConnect (Paid) and VPNC Front End (Free, Open Source).
sshuttle: where transparent proxy meets VPN meets ssh sshuttle is the only program that solves the following common case: Your client machine (or router) is Linux, FreeBSD, or MacOS. You have access to a remote network via ssh.
Front End to VPNC, a command line VPN client for Cisco VPN hardware. This client is known to work on: Windows 2000, Windows XP, Windows 2003, Windows Vista, Windows 2008 and Windows 7. It supports both 32 bit (x86) and 64 bit (x64/x86_64).
This is an open-sourced Secure Socket Tunneling Protocol (MS-SSTP) client for Android, developed for accessing to VPN Azure Cloud (or SoftEther VPN Server). So no test with other servers is done. Its behavior may be still unstable.