A long time ago lived in an apartment and used an openwrt router and some can-tenas to connect to the leasing offices guest wifi. Worked okay for about a year. Made sure to limit my torrents to after business hours. Then i was able to buy my own service so retired the setup.

Freespace 2 comes to mind. The whole game engine was open source not just the game itself. Looks like there is still a community building on it too. https://scp.indiegames.us/