Hi Joe,
The real bug is that this setting was showing up in module settings at all. I had changed this quite a while back so that it is only editable from the edit link not from module settings but must have missed something in an upgrade script along the way. It does work correctly from the edit page, but by design it only lets you choose a folder beneath /Data/Sites/[SiteID]/FolderGalleries and on the demo site I have the file manager locked down to the /Data/Sites/[SiteID]/media folder.
Because of the way this feature was designed it is needed to constrain the folder otherwise it could/would allow browsing file system folders that are beyond its scope. This feature came from a codeplex project that was not designed to plug into mojoPortal and was not designed to have any security or permissions of who could view the images.
I had considered changing it to locate the FolderGalleries folder beneath the media folder, but the problem is this would contain full size images not really suitable for use in web content. The feature generates its web and thumbnail images in a single location on disk for all sites under /Data/SystemFiles/FolderGalleryCache. There was not a way to make it have a different cache location for each site so there is not a good way to make the cache of web and thumbnail images browseable.
So to fix the issue about the setting showing up in module settings, this sql can be run:
DELETE FROM mp_ModuleSettings
WHERE SettingName = 'FolderGalleryRootFolder'
AND ControlType = 'Text'
The bug is that even though we changed it on the moduledefinition setting to not have a controltype it still had a lingering setting in mp_ModuleSettings with TextBox as the control type. By having an empty ControlType the setting will not appear in module settings, but it still can be accessed from code so we can edit it on the edit page and enforce checking that the entered folder name exists beneath /Data/Sites/[SiteID]/FolderGalleries
Best,
Joe