Thanks for your detailed response. I couldn't find an existing license out there that was suitable, so I'll have to get one drawn up by a lawyer. In the meantime, here are the answers to your questions:
1. An outward facing site means a website that offers unrestricted public access, i.e. not behind a password, firewall, hidden in an Intranet, etc... It means a site that anyone in the world can reach with a browser connected to the web. Perhaps the simplest way to say it is: a site that can appear in search engines.
2. You can modify the code as much as you want, and use that modified code on any website. You cannot however sell the modified code, remove the link to Q2A, or redistribute it. You don't need to share your changes, and can sell services to modify the code for others.
3. The license may change in future, yes, but the change will not be retroactive with regards to the current version being distributed. (I expect the license will only get less restrictive over time, but don't want to make a legally binding representation regarding that.)
4. Of course I reserve the right to pursue any violation of the license, and have already (unfortunately) had to do so in the case of two rip-offs.
Anyway I very much take your point about including a formal legal license. In the meantime I hope the above helps clarify things a little.