To expound, the OGL is a known quantity in the gaming community among established writers and publishers. The OGL is a quality license that offers protection to both companies giving away open content and those wishing to use that open content (you don't want anyone else using it, don't give it away, simple as that). It allows additional licenses to be placed ontop of it (i.e. d20 System Trademark License, Traveller Logo License, etc). It allows for the creation of whole new games. Wizards happens to be the one that wrote it so they get their name on it.
Some believe, myself among them, that the OGL is perfect and would like to keep using it for as long as we work with games. I'd guess that Mongoose shares my view (which makes me happy).