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 "=games-emulation/advancemame-5.0" have been masked.
!!! One of the following masked packages is required to complete your request:
- games-emulation/advancemame-5.0::gentoo (masked by: XMAME license(s))
A copy of the 'XMAME' license is located at '/Volumes/Disk 1/Repository/portage-git/licenses/XMAME'.


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