The file can be downloaded in the "See also" section of the above-linked web page. Should Safari append an ".html" to the file name during download, better remove it to prevent the local webserver from serving the page as html. I even just renamed the file simply to "man" here for less typing later.
Here's what you have to do to get it to work:
- Open the file in a text editor and find the line that reads $ENV{'PATH'} = "/bin:/usr/bin"; and add another line below that reads:
$ENV{'MANPATH'} = "/usr/share/man:/usr/local/man:
/usr/local/share/man:/usr/X11R6/man";
You might want to add additional man paths according to your needs (the line has been broken into two for narrower display; enter it as one long line with no additional spaces). - Put the file into /Library/WebServer/CGI-Executables
- Make sure it's executable (chmod 755 manServer).
- Start your local Apache via the Terminal or using Personal Web Sharing in the Sharing preferences panel
[robg adds: I tested this app out and it works as expected, and is actually very useful -- the hyperlinks are a nice benefit. I had to control-click on the download and select "Save to disk" to prevent Safari from opening it in the browser, but after that, installation was as described, including the renaming step.]

