Can i use mods

[KarateGuy]

I have the question before i use mod, and that is about that is "legal" to use it? The only reason is that i dont want to be banned from steam.

[daniu]

Yes, it's legal to use mods.
However, depending on what mods you use, you may be unable to play multiplayer games (except with people having the same mods I think).

[KarateGuy]

Okay but if i have a mod like The blue and gray can i so when i want to play the original game in multiplayer?

[KarateGuy]

Anyone who know about i can play and save the original game and play that campaign, while i can play a modded campaign?