Within the realm of merchandising, there is often what is considered to be licensed merchandise and what is considered inspired merchandise. Licensed merchandise is approved by the owner of the rights to a particular film, comic, character, or concept. In the case of Captain America and the Marvel universe, it is Disney. Disney holds the rights to the Captain America concept and imaging and, therefore, can sell the rights to retailers who wish to sell merchandise featuring Captain America. This often comes with a contract in which the retailer pays Disney for the ability to create and sell Captain America-related items. Inspired merchandise is a less restricted category. Within the area of inspired merchandise, everything is up to interpretation. While a retailer may not be able to write the words "Captain America" on their clothing, they could use the common term "Captain" with a red, white, and blue theme. This item would obviously be a Captain America item; however, because it did not use any trademarked images or names, it is not beholden to Disney and its licensing. Often you will find inspired merchandise to be more of an artistic representation of the character or universe they are sporting. So short answer, no; merch does not need to be officially licensed.