tinyE: One of these days someone is going to have to explain DRM-free Multiplayer. :P
It sounds like "water-free swimming".
This is so sad. You were born after 2000, right? That would explain it.
So here is the background: In times when not everyone had an internet connection, when you bought games on CDs, people where playing multiplayer games by carrying their computers to each others houses and connect them locally. You had to manually adjust the network settings of your computer to make it work. By the way, this is how I learned what ip address, subnet mask etc are.
Then the internet became something everyone had access to and it was also mostly fast enough to play games over it. No more need to carry computers around. But still there were no steam clients or the like. Some games were prepared for that, because you could simply enter the ip address of your friend's computer which was hosting the game on the internet and your computer would be able to join the game. For games which didn't support direct-ip, there was still the possibility to use tunnel services like hamachi or tunngle.
And guess what - these games still work today! Without the need of any server run by devs or other third parties. Tunngle still exists, as well and works perfectly. And Tunngle is already a convenience feature. You could just as well build a VPN or something similar to simulate a "Local Area Network" for the game.
TL;DR: No, multiplayer does not require DRM. Not even if you play games over the internet.