The OGL is based on the Gnu Public License (GPL). The GPL has been tested, I believe, in Germany but not in US federal court. There have been cases involving the GPL but none that directly challenge the GPL, if you know what I mean.
Most attacks on the GPL attack the concept rather than the law.
Licenses at heart are a simple concept: "You can use this thing to do X,Y,Z as long as you do/don't do A, B, C." The simplicity of the OGL helps defend it.
It prints out onto less than half a sheet of paper, even when using a normal font, and should be comprehensible to anyone with a 10th grade education. I'll trim out some of the more wordy sections and summarize.
1. Definitions: (Defines terms like "contributor", "trademark" and even "you" since lawyers are really anal.)
2. The License: This License applies to any Open Game Content that contains a notice indicating that the Open Game Content may only be Used under and in terms of this License. You must affix such a notice to any Open Game Content that you Use. No terms may be added to or subtracted from this License except as described by the License itself. No other terms or conditions may be applied to any Open Game Content distributed using this License.
3.Offer and Acceptance: By Using the Open Game Content You indicate Your acceptance of the terms of this License.
4. Grant and Consideration: In consideration for agreeing to use this License, the Contributors grant You a perpetual, worldwide, royalty-free, non-exclusive license with the exact terms of this License to Use, the Open Game Content. (If you agree to follow the OGL, you can use the OG content the license is attached to forever, anywhere, and for free.)
5.Representation of Authority to Contribute: (If you post OG content, you must have the right to license it under the OGL, meaning you are the copyright owner)
6.Notice of License Copyright: (Always include the copyright notices for everyone who's OGC you borrowed from.)
7. Use of Product Identity: You agree not to Use any Product Identity/Trademark/Registered Trademark, including as an indication as to compatibility, except as expressly licensed in another, independent Agreement with the owner of each element of that Product Identity. (In other words, you won't steal the iconic characters/places/things/names of other games or try to leverage them for your own use without a specific license allowing you to do so.)
8. Identification: If you distribute Open Game Content You must clearly indicate which portions of the work that you are distributing are Open Game Content.
9. Updating the License: Wizards or its designated Agents may publish updated versions of this License. You may use any authorized version of this License to copy, modify and distribute any Open Game Content originally distributed under any version of this License. (This is the legal "no-take-backsies" clause where the WotC staffers at the time made sure that no future WotC owners, like Hasbro, could screw the OGL)
10 Copy of this License: You MUST include a copy of this License with every copy of the Open Game Content You Distribute.
11. Use of Contributor Credits: You may not market or advertise the Open Game Content using the name of any Contributor unless You have written permission from the Contributor to do so. (Like #7, you agree not to use someone else's name to pimp your product.)
12 Inability to Comply: If it is impossible for You to comply with any of the terms of this License with respect to some or all of the Open Game Content due to statute, judicial order, or governmental regulation then You may not Use any Open Game Material so affected.
13 Termination: This License will terminate automatically if You fail to comply with all terms herein and fail to cure such breach within 30 days of becoming aware of the breach. All sublicenses shall survive the termination of this License. (Refuse to play fair and you become in violation of copyright law. Lawyers will be in touch, have a nice day.)
14 Reformation: If any provision of this License is held to be unenforceable, such provision shall be reformed only to the extent necessary to make it enforceable. (Which means that even if you strike down one aspect, odds are the OGL as a whole still survives)
15 COPYRIGHT NOTICE
Open Game License v 1.0 Copyright 2000, Wizards of the Coast, Inc.
