Which free game engines on Ubuntu would be the best choice for me to create 2D games. The engine should not be too hard to use and support multiplayer if possible. I'd use it to create games with graphics like TeeWorlds in combination with Inkscape ofc.
I have tried Löve which is one of the free 2D game engines I find very interesting. It's available at http://love2d.org/. It uses lua for the programming language.