Short answers, pulled from the story.
The Open Game License grants users a perpetual, worldwide, royalty-free license to use defined content. This legal agreement covers two distinct categories of material within any game system.
Wizards of the Coast published version 1.0 of this license in 2000. Ryan Dancey spearheaded this initiative to allow third-party publishers to create compatible material for Dungeons & Dragons.
Paizo announced a new Open RPG Creative License as a direct response to reported changes that made the previous license incompatible. The intent was to force compliance with the new agreement while maintaining a system-agnostic license not owned by any single publisher.
Greg Tito wrote for The Escapist in 2011 that this change took away freedoms the industry had come to expect. He argued that the shift removed essential rights previously granted under the original framework.