Which licenses are most applicable for themes within a web app?

Question

Suppose a developer is building a hosted web app which lets people use prebuilt themes on their websites. They can select and apply a theme, and they can also view and edit the HTML, CSS, and JavaScript source. The developer has built these themes from scratch. These themes are part of the app once a customer pays for access to the app, and they are only usable within the app.

This web app is not open source.

How can the developer legally prohibit any other competing app company from copying any parts of these themes and make them part of their own offerings within their own apps. The dev doesn't want another company to create the same sort of app and just copy over the themes s/he spent time building into any competing app.

Are there any suitable licenses?

Answer 1

Certainly none of the standard open source licenses will accomplish the desired end of prohibiting reuse of the HTML, CSS, and JavaScript source in other web sites and applications.

Such reuse is prohibited by copyright (and the source code is definitely protected by copyright) unless the copyright holder affirmatively grants permission. So simply being sure that a copyright notice is displayed when the editing window or dialog for editing the source is on view, along with a statement that copying and editing is permitted only for the purpose of modifying the individual user's interface to that app, or for inclusion in a site created using the app, and for no other purpose, should be sufficient. (Such a statement should also be included in a terms and conditions or EULA document, I would think.) This will not stop unlawful copying, of course, but it will make it clear that any such copying is unlawful, and that an infringement suit is possible.

If you are seriously concerned about such unlawful copying, you might be wise to register the copyright in the app in accord with the law of your country. If you are in the US, such registration is required to bring an infringement suit, and prompt registration (before infringement, or within 3 months of publication) is needed to get statutory damages and legal fees in any infringement suit.