Most likely that would mean that the farm practices traditional farming methods, customs and practices. For example a kind of working farming museum. An example would be the LSU Rural Life Museum.
Heritage farms may also be farms that have been farmed by the same family for over 100 years. This term and also refer to farms that specialize in the cultivation of heirloom plants or in raising heritage stock animals. These plants and animals are ones that may have been used as original stock for more modern versions.
Note: You'll often see heirloom tomatoes at the farmer's market or Whole Foods. These tomatoes provided the original gene pool for the tomatoes you see most often in the grocery stores. The same goes with beef or pork. The older (original) breeds may not have been hardy enough or fatty enough for today's market or today's ranching techniques, so their weaknesses were bred out and their strengths were bred in.
