Capcom has released a small patch for the Steam version of Resident Evil 5 that adds local split-screen co-op. This will allow players to play with a friend without both needing their own computer or a copy of the game. Games for Windows Live are no longer supported in Resident Evil 5. (Thanks, Wario64!)
Local split-screen co-op is literally what it says on the box. As long as there are two controllers both players can play with, you will be able to cooperate with a friend on the same system. However, the screen will be smaller as a result. This was the offline co-op method that Resident Evil had implemented in the past, such as in the original console iteration of Resident Evil 5.
As for Games for Windows Live, it was a gaming platform that was originally released during the Xbox 360 era. When Windows was no longer officially supported, some publishers l were always. However, this will no longer be the case for Resident Evil 5. Players who were still using Games for Windows Live for Resident Evil 5 will no longer be able to do so after this patch.
Resident Evil 5 is available on PS4, Xbox One, Nintendo Switch and Windows PC via Steam. Starting with this patch, PC players will also be able to play offline split-screen co-op. The same patch also fixed several minor bugs and issues.