Just from looking through the .deb you posted: all the files in it are owned by root, which might make sudo necessary. As a download manager escalation shouldn't be required. You can either 'chown user file.extension' all the project files, or 'chown -R user directorywhichyoupackaged' before dpkg-build to change ownership to user. Shouldn't require sudo then (then again, not sure if scratchbox will allow that, on device should work, so postinst chown might be a better idea, someone with experience with SB could chime in)