§ 23399.1. (simplified)
No license or permit is needed when:
1. There is no sale of alcoholic beverages. (Host provides the drinks, there is no cover charge and drinks are complimentary for guests)
2. That the premises are not open to the general public during the time alcoholic beverages are served, consumed or otherwise disposed of. (The event is only for invited/a limited number of guests)
3. That the premises are not maintained for the purpose of keeping, serving, consuming or otherwise disposing of alcoholic beverages. (The venue's general purpose does not include the consumption or serving of alcohol)
A permit is needed for all types of events where alcohol is served unless the event is strictly private (e.g. a family event).
According to the New York State Liquor Authority Permit Unit, a special events permit is generally required for any public or corporate events "where alcohol is served, sold or consumed at an event and location."
"Generally the only time a permit would not be required would be [...] for invited friends and family a[t] a private residence."