http://www.sencha.com/legal/open-source-faq/
For example: let’s take a mortgage processing software program. Let’s say that the application has a front-end (that generates web pages linked to Ext JS JavaScript) that communicates over JSON/HTTP with a backend service. This backend service contains approval and validation logic for this application alone. Even if only the front-end uses Ext JS code, you should consider that the combination of front and back ends constitutes the application, and the source code for both back and front end would need to be provided to the application’s end users under GPLv3 if the application is used by an end-user who is not part of the same legal entity that holds the GPLv3 license to the Ext JS code.
Next, let’s assume that the mortgage application web-pages also offer functionality that allows users to search current interest rates, and file a customer support ticket (functionality ancillary to the purpose of the application) and those functions are provided by s