It is legal to provide free alcoholic beverages without a permit. However, to be truly “free,” it must be available to any adult who walks in the door and requests it. If alcoholic beverages are only available to paying customers, the assumption is that the cost of the alcohol is included in the price of the service. This constitutes a sale of alcoholic beverages, and a TABC permit would be required. When you provide the alcoholic beverage, there cannot be any expectation of receiving money. You cannot ask for a “donation” or “tip.” If the drinks will only be available to paying guests, then you will need a permit.
Some examples: A wedding reception with free drinks is really free. A boutique that serves free wine while you shop, even if you don’t buy anything, is really free. A nail salon with a “free” drink when you pay for a manicure is not really free. If you buy tickets to attend a charity ball and they serve “free” drinks, those are not really free. If a tip jar sits next to a keg of beer expecting “donations,” the beer would not be considered free.
from the Texas Alcoholic Beverage Commission – FAQ page