They are known for the Kingdoms of Kalamar campaign setting and for their own HackMaster and Aces & Eights: Shattered Frontier role-playing games (RPGs).
[1] In 1994, Kenzer & Company released The Kingdoms of Kalamar, a fantasy campaign setting compatible with Advanced Dungeons & Dragons.
[3] Shortly after Wizards of the Coast announced the 3rd edition of Dungeons & Dragons, they announced jointly with Kenzer & Company that Kenzer had acquired a license to produce official Dungeons & Dragons material, using the Kalamar setting exclusively.
With the release of the fourth edition, Wizards of the Coast introduced its Game System License, which represented a significant restriction compared with the very open policies embodied by the OGL.
The Dungeons & Dragons trademark is used in accordance with US law under a concept called nominative use – the book merely says that it is for use with the new version.