Most have been developed and generously donated by members of the wider Zen Cart community. The Classic Template is bundled as part of the current Zen Cart release (1.3.9d).
Yes. That's part of why they're there. Some of the graphics may be copyrighted. See the Zen Cart Support Site's FAQ for more information on this. And hopefully you will also use the templates as a springboard from which to create your own original designs.
Most of the available templates are included. Templates have been excluded only under the following circumstances:
Yes and no. The templates have been installed in strict accordance with the installation instructions supplied by their designer (and included in the zip archive for each template).
That depends on the error. Most templates are reasonably robust and problems have tended to be limited to cross-browser issues. These have been less common in recent years as browsers (especially Internet Explorer) have become less buggy and more standards-compliant.
For more specific problems we sometimes help the designer to fix the problem, sometimes they bring solutions to us. In both of these cases the solution is only reflected on the demo system if the designer uploads a new release of their template to the Zen Cart forum for use by the whole community.
If a problem would make a template dangerous for use by new Zen Cart users, we don't put it up, and we recommend to the Zen Cart team that they withdraw it from the forum downloads area too.
So what you see on this site is as close as we can make it to what you would get if you downloaded and installed the template yourself.
Provided it hasn't been excluded for one of the reasons listed above (see the answer to "How did you choose which templates to include?" then we may have missed, or just be a bit behind with our updates.
Feel free to send us an email with details of your template and we'll get on it.
That might change one day, we have considered allowing the promotion of good quality templates, well-implemented templates on this site.
But currently, this site is exclusively for demostrating the templates donated to the Zen Cart community.
We can't speak for all the designers, but suspect that most would suggest that you make a donation to Zen Cart to help encourage its continued development. You can do that following this link.