[Dean C]

Originally Posted by Simetrical

The major advantage of using an established license is that people usually have a clear understanding of what exactly it means. If you really don't want the same functionality as any existing license, could you at least phrase it as a diff to an established license? Like the suggestions here. E.g., release it under the LGPLv3 or later, except with additional requirements like "You must provide any modified versions to vBulletin upon request even if you didn't distribute them", or whatever.

Yep, this is exactly what I was getting at.

I don't work on open source projects unless they use an established license without extra conditions. This makes it simpler for everyone as we already know how the license can be challenged and how it can protect author works.