Game-wise, there's no difference between the two aside from the one signing in using Steam and the other via the launcher. The Nerdkingdom accounts were a means for our Kickstarter and other very early backers to authenticate and download TUG Early Access before we were Greenlit on Steam. The two account types are currently not connected, but we do plan to merge them, as well as the forum accounts into a single sign on account in the future.