When you try to uninstall Simple Survey you most likely will encounter two errors preventing you from doing so. There is a Force.com site reference and permission set that need to be removed before Simple Survey can be successfully uninstalled.
Removing Simple Survey from your organization will result in an Unable to uninstall package error.
The Simple Survey Site Guest User is given access to the Simple Survey Manager (CRED) permission set. You will need to remove this permission set.
A Simple Survey Visualforce page is used by the Site that was setup for the survey. You will need to remove the Visualforce page and deactivate the survey site.
If you have installed the Simple Survey extension package, which contains workflow rules to automate survey delivery, you will also see a third error related to this package. Simply uninstall the extension package before attempting to uninstall Simple Survey.
Simple Survey will now uninstall. If you continue to have issues with uninstalling Simple Survey, please contact firstname.lastname@example.org.