The OpenVPN Connect clients for iOS and Android are based on the OpenVPN 3.0 code which is publicly licensed under the AGPL and available here:
http://staging.openvpn.net/openvpn3/
Note that OpenVPN Tech. cannot release the code that implements the integration between OpenVPN and the iOS VPN Framework because it's under NDA.
Regarding the issue of GPL requirement to disclose source code, this is only a requirement if you are using other people's GPL code. If you are the copyright holder of a body of work, you are free to license or relicense it in any way as you see fit.
James