"Federal prosecutors successfully argued that von NotHaus was, in fact, trying to pass off the silver coins as U.S. currency. Coming in denominations of 5, 10, 20, and 50, the Liberty Dollars also featured a dollar sign, the word "dollar" and the motto "Trust in God," similar to the "In God We Trust" that appears on U.S. coins"http://en.wikipedia.org/wiki/Liberty_DollarNot that wiki is the end all in reliable sources but it doesn't seem there's too much question here.
It's the sign and the dollar that are the main problem. Anyone can place God we Trust or whatever on it. The Dollar is the US corporate currency created by the private international banksters.