Obligatory Icosahedron Licensing, or OIL, was a scheme concocted by Magicians of the Bay which allowed third-party publishers to create their own Icosahedron games compatible with the latest edition of Labyrinths & Lamiae. One such company was Death Lord Games.
Unfortunately a hidden clause in the OIL license meant that all licensees owed MotB license fees backdated to the release of Boiled Leather, the original L&L rulebook. This destroyed most companies, but Black Dog was saved by computer company PCP Games.
Background Information
The OIL license is a parody of the D20 System Trademark License and/or the Open Game License. While Wizards of the Coast allowed any company to use the license free of charge as long as they adhered to the terms of the d20 license, presumably MotB get a moderate kickback from use of the OIL license.