No data is transmitted to the developer or any third party. Information gathered is stored in the app database and backed up in your iCloud account, shared only on your other devices where this app is installed and is logged into the same iCloud account.
Access to the photo library is required to enable journaling of photos and videos. You can provide full access which will allow the app to retrieve all photos within the dates of the journal you are creating. Limited access works but it requires that you preselect the photos for the journals every time you want to create or add to a journal.
The location information comes from the photos, provided you allowed that information to be captured at the time the photo was taken. The app does not access your current location, nor does it track or share your photo locations with the developer or third parties.