Hello bez,
I suggest to check that you are following proper installation steps:
- download DMG archive from our web-site,
- open DMG (that's the point when you need to accept the license conditions) and move PhotoScan (and Lens if necessary) application bundle to the /Applications/ folder. So do not move DMG itself, just PhotoScan.app from the unpacked DMG archive,
- run PhotoScan application bundle from the /Applications/ directly or using the shortcut.