Actually, they are just like gm moves, so no dice are involved. You spend hold and the move happens, period. You already rolled the dice in the first place just to perform the shapeshift, so there's no need to roll again.

This is my understanding as well.  Because Hold is a specific resource, it's expenditure is the "opportunity cost" of the Move in question, so therefore, having another roll on top of that -- which could fail, and thus negate the whole point of spending Hold, which is a valuable and limited resource -- seems like it would penalize the mentality of using such a Move.

My understanding also comes from how Heritage Moves in Dark Heart of the Dreamer work.  In lieu of a standard race-based move from your Class, you can instead pick 2-3 "Heritage Moves."  At the beginning of a session, roll +something or other, and you get 1, 2, or 3 Hold based on the roll.  You can then spend the Hold to make a Move, and the Moves listed come straight from various Monster Moves -- which are automatic -- or something of that sort.  Point being, you only have maybe 1, 2 or 3 Hold for an entire session to spend on these Moves, so you shouldn't be penalized by spending the Hold and then having the Move fail.

Just for reference, I'm working on a conversion of "Kill Bargle!" -- first D&D adventure in the famous D&D Basic Set Red Box, later updated in Dungeon Magazine #150 -- and have posted it to my blog.

Once the players have their characters done, I'll post a Part 2 to follow up on how things evolved based on the Players' input.  It's already shaping up to be wildly different, yet based on the ideas and maps from the original.  It's pretty amazing how DW can change things up without negating things.