Cloning B/X

The Basic Rules as edited by Tom Moldvay is legendary across the hobby as one of the cornerstone and premier versions of the World's Most Popular Role-Playing Game. Many gamers have come to the hobby through the "Moldvay Basic" rules, which remains the preferred dungeon delving rule system for many. Frequently referred to as B/X (the second volume in the series is the Expert Rules edited by David "Zeb" Cook with Steve Marsh), the Tom Moldvay Basic Rules remains one of the most popular interpretations of role-play rules and is still in popular demand 38 years after its introduction. The Basic Rules, published by TSR includes rules for character levels 1 to 3 and requires the Expert Rules to advance character beyond 3rd level. The B/X system supports human characters with the Fighter, Cleric, Magic User and Thief class. The demi-humans (dwarves, elves and halflings) each have their own class.

The continued popularity of the B/X system despite its being out-of-print leads to one of the first retro-clones to appear as part of the "old school renaissance" or OSR movement. Labyrinth Lord by Daniel Proctor uses the System Reference Document under the Open Game License to create a game system very close to the original Basic/Expert Rules thereby allowing authors in the OSR to publish new material which is fully compatible with both Labyrinth Lord and therefore the originals. Part of the beauty of the original editions of both the Basic and Advanced Games is a cross compatibility allowing the hobbyist to use play aids written for one version of the system with all the other versions. This remains true until the 3rd edition (and later) published by Wizbros.
Labyrinth Lord itself exists in several printings with a variety of cover illustrations (and there is a free digital version as well). The latest iteration is titled Advanced Labyrinth Lord and combines the original Labyrinth Lord based on basic/expert with material from Mr. Proctor's Advanced Companion - a volume that adds in additional classes, spells and monsters similar to TSR's Advanced Game and provides for the separation of character "race" and class as found in the Advanced system. The image above shows one of two covers currently available as a print-on-demand hardcover of the Advanced Labyrinth Lord.
The OSR is a creative and hard working group and they have produced a number of system variations using the B/X model as a basis. Notable mentions in this category from my personal collection include Lamentations of the Flame Princess, Basic Fantasy and most recently B/X Essentials.

Lamentations... is an awesome adaptation of the B/X core heavily impregnated with the character of its creator, James E. Raggi IV (word choice is deliberate and if you are familiar with LotFP you know why). Mr. Raggi subtitles his work as "Weird Fantasy Role-Playing" and anyone familiar with the books will understand why. Lamentations... may not be to everyone's liking, but the changes Mr. Raggi makes to the standard B/X rules produces an unmistakable tone and includes many good ideas ( such as encumbrance and specialist skills).

Basic Fantasy is a Chris Gonnerman game based on the B/X model while incorporating many newer conveniences. BF is incredibly playable and one of the better introductory RPG systems with years of play-ability. It has the added advantage of being priced so as to be about as good a bargain as one could ever hope for. Mr. Gonnerman has supported Basic Fantasy with a library of well written supplements and play aids. There is literally no reason that a copy of Basic Fantasy should not be in every FRPG hobbyist's collection.

B/X Essentials is a print on demand product by Necrotic Gnome. Essentials reorganizes the cloned B/X system material into several volumes, each of which is the small digest size used by the White Box. Volumes include the Core Rules, Classes and Equipment, Cleric and Magic User Spells, Monsters and, Adventures and Treasures. The modular organization allows for a seamless combing of levels 1-3 and 4-14 from the Basic and Expert Rules respectively and for the substitution of any new module such as replacing the Classes and Equipment book with one more directly aimed at your campaign. In many ways, the B/X Essentials: Core Rules is closest to the original Moldvay/Cook/Marsh game and also the most adaptable (B/X Essentials: Demihumans of Dolmenwood is an add-on for the Dolmenwood mini-setting). For do-it-yourself enthusiasts or those seeking a well organized B/X feel, Essentials is also a good choice.