Gnu-info page exists, but is visible from neither emacs nor terminal
Is the info file symlinked in /usr/local/share/info? If not, a simple

ln -s /usr/local/Cellar/gnuplot/4.4.3/share/info/gnuplot.info /usr/local/share/info/


should solve the problem.

If not, look at the value of Info-directory-list in Emacs (C-h v). If "/usr/local/share/info" isn't included there, you can add it with

(push "/usr/local/share/info" Info-directory-list)


in the *scratch* buffer (and in .emacs of course).