According to the dictionary, one set of definitions of 'license' is
"1. Lack of due restraint; excessive freedom: “When liberty becomes license, dictatorship is near” (Will Durant).
2. Heedlessness for the precepts of proper behavior; licentiousness."
The definition of 'license' that is synonymous with 'licentious' evolved from a very different definition:
"1. a. Official or legal permission to do or own a specified thing. See synonyms at permission.
b. A document, plate, or tag that is issued as proof of official or legal permission: a driver's license.
2. Deviation from normal rules, practices, or methods in order to achieve a certain end or effect."
These meanings are derived from "Middle English licence, from Old French, from Medieval Latin licentia, authorization, from Latin, freedom, from licens, licent-, present participle of licere, to be permitted."
License in the context that I want to focus on in related definitions such as libertarian
is the lack of proper restraint or licentiousness.
Defenders of liberty have traditionally gone to great lengths to distance liberty from license. Tragically, modern leftist liberals and modal libertarians have conflated the the two. License is a perversion of liberty that has morphed into its opposite.
Modal libertarian: I love to exercise my liberty by watching some porn while I smoke pot.
Paleo-libertarian: You are confusing liberty and license.