From the introduction:
This module was inspired by the re-release of the Moldvay Basic Edition of the world’s most famous FRPG and is the culmination of a project to imagine what that Basic Edition would look like had the monster section only included creatures found in my favorite folio of fiends (often referred to as the FF). Since the boxed set of the Moldvay Basic Edition came with the second installment of the B-series of adventure modules, it follows that I should re-image that introductory module as if it would have appeared in the FF version of the Moldvay Basic Edition.
This adventure is written for the retro-clone Labyrinth Lord™, an excellent emulation of the Moldvay Basic Edition. Therefore, this adventure is not only compatible with that edition, but requires almost no conversion to use with any of the older editions of the world’s most famous FRPG.