Hello grampae,
OpenVPN Access Server is a closed-source program and the license forbids that:
"You agree not to reverse engineer, decompile, disassemble, modify, translate, make any attempt to discover the source code of this software, or create derivative works from this software."
If you're interested in the OpenVPN core that handles the VPN tunnels themselves, that is fully open source and available here:
https://github.com/OpenVPN
Kind regards,
Johan