i hope other people address this too. my sense of market anarchism is that it could be/is sometimes anarcho-capitalism lite, depending on who you talk to, and how you define capitalism and market.
i believe there are market anarchists who are not capitalists, and who call themselves that because they have a specific emphasis (as with sindicalists, for example... edit (sigh) i mean that sindicalists focus on workers and work, and the tendency is named for that). what they focus on in when thinking about how anarchy could work is markets and currencies and trade, and they support the idea of some kind of market place, which (at its most benign) could be a town square where people trade stuff, for example.
as always, i look forward to more knowledgeable people correcting me.