Well this recipe seems to be relying on both natural ("wild") yeast to start the mead, and then on natural acetobacter to make it into vinegar. This also assumes (but doesn't tell you) that the mead has access to oxygen, which the acetobacter need to convert ETOH to acetic acid.
The container doesn't matter; as long as the (eventually fermented) mead somehow gets inoculated with a vinegar mother after fermentation, and then typically some cheesecloth over the top so it can "breathe".
Bees, brews and fun
in Lyons, CO