But games require huge server infrastructures to run: Only applicable if it's a massively online multiplayer game. If your game requires thousands of people to be connected to the same game world at the same time - then your argument does hold water. If your games only requires a handful of people to play, it's not hard to host a server. People are not stupid or computer-illiterate. There are games older than I am that are still enjoyed all over the world - because people host servers all by themselves. Don't give us this patronizing crap.
Then there's also single-player games. Those require no server infrastructure AT ALL. So shut fuck up.
And, by the way, theoretically, you can make a federated game server. It's a huge undertaking, but it potentially can make your MMO game immortal. Not that you're interested.
But security and cheaters: If your security relies on obscurity, guess what: it's bad security. If releasing your protocol documentation means that the security of the game will be compromised, guess what - your protocol sucks and it is vulnerable, whether you release the docs or not. At the end of support you aren't going to fix it. Maybe we can then. Trust me: community effort weeds cheaters out very efficiently where it matters.