Android VPN app based on OpenVPN library.
I use free OpenVPN configuration file from this site https://www.vpngate.net/en/
I am not sure how long it will work with the free ovpn file. It's better to update ovpn files with your own ovpn.
This project and the uses VPN library "ICS OpenVPN" both are under GPLv2 License.
Make sure you understand the licenses of the code. OpenVPN for Android is GPL licensed.