Here is a good page describing the situation, from the MPAA.
The Good News? It's Easy to Obtain a Public Performance License?
Obtaining a public performance license is relatively easy and usually requires no more than a phone call. Fees are determined by such factors as the number of times a particular movie is going to be shown, how large the audience will be and so forth. While fees vary, they are generally inexpensive for smaller audiences. Most licensing fees are based on a particular performance or set of performances for specified films. The major firms that handle these licenses include:
Swank Motion Pictures, Inc.
Motion Picture Licensing Corporation (MPLC)
In other specialized markets, such as hotels and motels, many Hollywood studios may handle licensing arrangements directly.