Are there certain businesses or sites that are prohibited from using InviteBox?

YES,

The widget may not be used on websites that contain pornographic or adult content, racist, discriminatory, defamatory, libelous, harassing, threatening or otherwise objectionable content, violate copyright or trademarks, are set up for the distribution of chain letters, Ponzi schemes, multi-level marketing systems, that contain malicious content such as spyware or viruses or that otherwise violate U.S. or locally applicable law. In addition, the widget may not be used on websites that promote the sending of unsolicited commercial messages (‘spamming’).

when in doubt, please contact us so you will not have your account cancelled.