These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.83 s (backtrack: 0/20).


!!! All ebuilds that could satisfy "=mate-extra/caja-dropbox-1.28.0" have been masked.
!!! One of the following masked packages is required to complete your request:
- mate-extra/caja-dropbox-1.28.0::gentoo (masked by: CC-BY-ND-3.0 license(s))
A copy of the 'CC-BY-ND-3.0' license is located at '/Volumes/Disk 1/Repository/portage-git/licenses/CC-BY-ND-3.0'.


For more information, see the MASKED PACKAGES section in the emerge
man page or refer to the Gentoo Handbook.