GraphicsMagick is a replacement for ImageMagick. Now dev-php5/magickwand depends only on media-gfx/imagemagick.
First: thanks for the information.
Second: magickwand uses the MagickWand-config utility, which gets installed with imagemagick, but not with graphicsmagick.
Upstream explicitly names imagemagick as a dependency. Even if graphicsmagick is a complete stand-in, please address the issues in the blocking bug first, dealing with the differences between imagemagick and graphicsmagick. If they are resolved, I will gladly take patches for config.m4 or produce one myself.
Please reopen this bug when that's done. Thanks.