Defining Terms: How to differentiate between various flavors of d20 D&D

[Ranger REG]

so if a product is describing itself could it use the phrase "d20 OGL"?

Or "d20-based OGL," like it's printed on the front cover of my A Game of Throne RPG.

 

[Ranger REG]

Call me thick perhaps, but what's the end-result difference between d20 and OGL material anyway, if written for the same game e.g. D+D? In other words, if I pick up a book written for D+D and start reading it, would I be able to tell the d20/OGL difference if I ignored the legalese and cover symbols?

Should it matter to the readers who are not aspiring game designers? The things that should matter to the readers are the quality and usefulness of the game product that can make or break the publisher and the designer(s).

As I stated before, if the product has a trademarked "d20 System" (the little red-n-white square with black border), it means you need the Player's Handbook. Such a product has little deviation due the the restriction in the Trademark Usage Guide. It's for the reader's convenience.

What matters more for discussion purposes is whether a given thing is written for D+D, or for Star Wars, or whatever game, to put it in context.

If something is written for D&D, it should say so, or at least be "compatible with any d20 fantasy games."

For Star Wars, you can't make any connection whatsoever without infringing on Lucasfilm. HOWEVER, if you're a rules tinker, there is nothing to stop you from importing mechanics from one product to another game ... for personal or group use.

d20 System is modular. You can add or swap new [OGC] mechanics, with little or no difficulty into another game using the d20 System rules.

For examples, I never did like the autofire rules in Star Wars, so I replace it with the autofire rules in d20 Modern.

I never like WotC's psionic rules, so I used the Psychic System rules from The Psychic's Handbook from Green Ronin.