A business license was an authorization by the Ferengi Commerce Authority (FCA) for Ferengi businessmen.
When Quark was forced to break a contract with Brunt, Brunt responded by revoking Quark's license. A year later, Quark was able to get his license back. (DS9 episodes: "Body Parts", "Ferengi Love Songs")
Hilt's business license was granted by the FCA in 2385. (DS9 eBook: I, The Constable)