vTunnel can be used to add bridging over the internet to any existing OpenOS software that uses linked cards.
Despite originally being written for Minitel, vTunnel implements a fully-functional linked card emulator and a server that will run under most unix-likes (OpenBSD is currently somewhat flaky, Linux is recommended).
You can peruse the page on Github, for documentation and protocol information.
Install it with oppm:
oppm install vtunnel
Additionally, you can read the documentation in-game with