If you would like, I could help you out. I am currently a server Administrator for a big Modded Minecraft Community and always willing to make friendships. :)
Very odd they would outright ban crafters. That is really what the mod is meant for. Could you be a little more specific on what you want to try to do?
I can confirm that this is a problem in singleplayer and multiplayer. The multiplayer server I help run does use sponge but that isn't the issue. This looks like a problem in the scripts folder in the tinkers.zs file. This is the file that adds the smelting in the Tinker's smeltery recipe to...