Ok, I was planning on getting the Ars Magica Mod, when I recalled a rule about no modded clients. Does modded client mean having a mod such as the Ars Magica Mod?
Modded clients are allowed, but, some mods are illegal. When you're not sure about any mod, don't hesitate to ask one of the staffmembers, or make a thread in the help support section. Ars Magica is allowed, btw.
Yes, but it's not limited to those. There are many illegal mods, specifically the mods that give an unfair advantage (like minimaps with player/entity radar, caveview, etc) and hacks (like x-ray, fastbreak, etc)