ExpressVPN, a free VPN service, embeds OpenVPN and LZO inside its iOS application.
These two pieces of software are both licensed under GPL. To my understanding, ExpressVPN must make source code available because of these licenses. I have emailed ExpressVPN asking for the source code of their iOS app, but they have not replied for multiple days.
Is ExpressVPN required to share the source code, or am I misunderstanding the GPL?