TcpNoDelayMod improves the client's network connection by disabling Nagle's algorithm. This mod has no effect on Minecraft version 1.8.1 and newer, as Mojang has already made the same modification.
Simply place the jar file in your forge mods folder as you would with any other forge mod. Delete the jar file to uninstall the mod.
Note: TcpNoDelay will NOT appear in your forge mods list.
No. The changes this mod makes are in the TCP layer, Minecraft servers should not be able to see any difference. Also this change is already present in Minecraft version 1.8.1 and newer, meaning it's perfectly ok.
Please see the readme in the GitHub repository for some more technical details.