A user was curious what happens to data that they built with Skuid if they have to uninstall the app in the future

To my best understanding, once you delete the app, all data would be deleted including the XML created for the Skuid Pages developed. If a user wants to save their XML data they can do so easily using the Skuid application. This will allow the user to reuse the Skuid Pages they developed at a later date (either in the same org or a different one).

Skuid removes Skuid Page & Page Assignment records during the install, but not necessarily static resources used by the implementation (like JavaScript files). So it should be backed up before uninstalling. Also, during the uninstall Salesforce gives the option to receive a backup on successful uninstall. However this disappears after 48 hours so it needs to be saved before then.