This is not a server side app. This is a command line script.
If you have xampp and/or run redhat , drop to the prompt, cd to the dir and type
php xrns2midi.php /path/to/file.xrns output.midi
The file(s) will be created in the current working directory. On windows you need infozip (unzip.exe) to get this to work. See this thread for more info:
I run OS X myself. It’s all about bash shell. 