Thank you for responding. And don't worry about not being a lawyer, neither am I. (mainly because I don't want the responsibility; I am the kind of person who reads legislation for fun...)
As far as I am concerned, once both spirit and letter of the terms are known, I'll abide by the terms. I have spent enough time around lawyers to know that a case like this could easily cost into the tens, if not hundreds, of millions because of the potential impact on the industry, which I don't have, and Stardock have one of the most end user friendly positions anyway (it's vastly better than EA's, that's indisputable) so it is the wrong game to have that kind of case with.
As far as actually selling anything goes, that would only be done with things that I know I have the rights to sell - and the way I'm thinking is that only the written works and associated specifically commissioned artwork would be packaged in a paid-for thing, as that way it avoids the issues. I'd likely not sell anything as that reduces the complexity greatly.
With GC3 and similar, any distribution of gameplay content would purely be for free.
I wouldn't say grow my own ideas - I already have them, have done for over two decades in some cases. It is documenting them that I am thinking of using GC3 for, because the tools available in GC3 are far superior to what alternatives I have. But the distinction doesn't really matter.
You are right that the licence, certainly for player created content, is indefinite:
"2. Create "mods" based on the documented functions of the SOFTWARE to customize it. Distribution of your Mod in any form constitutes a grant by you to Stardock of an irrevocable, perpetual, royalty-free, sub-licensable right to use, copy, modify and distribute that Mod (and derivatives of that Mod), and use your name if we choose to, for any purpose and through any means, and without obligation to pay you anything, obtain your approval, or give you credit. You also agree to promptly execute assignments confirming this license upon request from Stardock."
Effectively it's saying Stardock have equal ability to use player created content once a player has released it, which is the same as the way the player can use Stardock's content, which is fundamentally fair to both parties.
By contrast, this is the equivalent section from EA's licence that shipped with Spore:
"A. Reservation of Rights. You have purchased a license to the Software and your rights are subject to this License. Except as expressly licensed to you herein, EA reserves all right, title and interest in the Software (including all characters, storyline, images, photographs, graphics, animations, video, music, text), and all associated copyrights, trademarks, and other intellectual property rights therein. This License is limited to the intellectual property rights of EA and its licensors in the Software and does not include any rights to other patents or intellectual property. Except to the extent permitted under applicable law, you may not decompile, disassemble, or reverse engineer the Software by any means whatsoever. You may not remove, alter, or obscure any product identification, copyright, or other intellectual property notices in the Software. EA owns all of the right, title and interest in the Software; to the assets included in the Software for building and animating creatures and for creating backgrounds and video clips; and to all derivative works comprised of those assets, including the Spore creatures that you create, animate, and capture in screen shots or video clips using the Spore Creature Creator. You may use only the assets supplied with the Software and the Spore Creature Creator to create Spore creatures and related assets. You may not further modify Spore creatures with any other materials, tools, or software programs. All rights not expressly granted herein, are reserved by EA." (my bold added)
And this is massively different, this kind of language means someone in my position risks being sued for copyright infringement, which is why I want to clarify the subject. About the only defensible point here is the fact that they used the same one for the Spore Creature Creator software as they did for the Spore and Spore Galactic Adventures games, because those feature far more creation tools, however that changes nothing for me as the creature creator parts are what I would have been using it for... I'll just have to use 3DS Max or something.