Hello,
i would ask you to remove Yap as a Windows program. It does not seem, as an exe file could be downloaded.
Also there is no MacOS Xpdf GUI version, so that link should be removed too.
KPDF (did not see it anymore in kdegraphics) should be removed as well, to me it seems Okular has replaced it completely.
For MacOS i found more PDF readers, but i don't have an Apple machine: - http://skim-app.sourceforge.net/ - http://code.google.com/p/formulatepro/
http://www.uoregon.edu/~koch/texshop/ would require multiple installation steps, so it might no be that useful for regular users.
http://wwwthep.physik.uni-mainz.de/~plass/gv/ was last updated 1997, so does it make any sense to still have it in the list? The latest version of http://home.gna.org/gsimageapps/ is already from 2005 ;)
You can check popularity for the different platforms via: Windows: http://alternativeto.net/desktop/adobe-reader/?license=opensource&platfo... Mac: http://alternativeto.net/desktop/adobe-reader/?license=opensource&platfo... Linux: http://alternativeto.net/desktop/adobe-reader/?license=opensource&platfo...
Feel free to add BePDF, MuPDF, Xpdf and Yap to the site if you like.
Best Regards Stefan Furtmayr