There are plenty of private currencies in the U.S [1]. Printing them and using them are just fine as along as A) you do not attempt to pass it off as Federal currency and B) you do not refused to accept renumeration in Federal currency (the "for all debts, public and private" part) without pre-stated agreement. We agree you will mow my lawn and I will pay you 50 Disney Dollars, that is fair and legal. That said, the person doing the mowing the law owes income tax on the fair market value of the Disney Dollars.

[1] https://en.wikipedia.org/wiki/List_of_community_currencies_i...