This directory contain 3 files:

NOPBetaWin.zip is the NOP zip archive for Windows (tested under Windows 98 and Windows NT).
NOPBetaLin.tar.gz is the NOP tar.gzipped archive for Linux.
NOPBetaLin.tar.bz2 is the NOP tar.bz2 archive for Linux (smaller by about 25% than the tar.gz one).

Download the one that suit to you. Uncompress it in the directory you like to install NOP, then follow instructions and recomandation included in README.txt file you will find in it.