Another solution would be to add a /opt/local/gnu directory, with (at

least) bin and man subdirectories for GNU utilities. The files with

the g prefix would still be installed in the standard place IMHO, but

the files without the prefix would be installed under /opt/local/gnu.

Then the end user could choose to add /opt/local/gnu/bin to his $PATH

before /opt/local/bin if he prefers the GNU utilities, or after if he

prefers the other ones. If for some particular commands, he wants a

different choice, he can still add a symbolic link into /usr/local/bin

or $HOME/bin...