I found very little information regarding client side mods (other than Optifine, Shaders, and a Shulkerbox viewer) and was wondering if a structure template mod would be allowed on the server. The specific mod that I'm inquiring about is Litematica (
http://www.9minecraft.net/litematica-mod/) which allows the user to bring templates or blue prints of a structure from a saved world and virtually place it on another world, in this case; Zedwork, (rather than going back and forth between two open Minecraft windows tediously). As this mod is client side, it only is viewable and usable by the viewer. If this type of mod is prohibited on the server I will refrain from using it and continue using my previous method, the mod is just convenient for me to use as I use it regularly on my single player worlds.