The source site content is only used to populate the site the first time. Therefore changing the source site to a different site will have no effect, since the user would have confirmed their settings via the goMobi Setup Assistant. If they have not confirmed their settings, then content from the new source site will be available in minutes.
If the goMobi site includes links to content on the source site, then changes to the content on the source site have immediate effect on the content of the goMobi site.
If you are using goMobi designer's toolkit and have to modify the source site (such as adding a class to the link in the source site), the goMobi site would have to be reset and the domain crawled again in order to see the change.