I'm asking for this for Christmas

For some reason I have neglected to get this game. I have always thought it looked absolutely amazing but for some reason I never thought of getting it.

That was until I got the demo for it. And oh my god, I can't wait until Christmas to get it.

I have some questions though..

So I know that this game has no DRM or anything. But can I simply install the same game on multiple computers and play LAN with them? My friend is very stubborn when it comes to games and he doesn't seem to want this game very much but I'm going to make sure he will change his mind. So I want to install it on 2 computers and play LAN with him. Is it possible to do that?

Also, can someone with the entrenchment expansion pack play with someone who does not have the expansion pack? Just in case my friend and I get different packages of the game.

Thanks.