Netscape browser, once dominant, is now in a challenger position in front of Microsoft Internet Explorer. Its remains anyway a major player, in particular with its version 6.
Netscape is accessible from its Downloading Page. From this page, you have to follow a lengthy selection process (language, operating system, etc.). It is impossible to give the complete address because this access path is calculated on the fly and includes the date of the day.
It is also possible to download from the FTP site, where the same selection process should be made. Last time I checked, I could not find the Macintosh versions any more.
At some point, you have to select the operating system, the downloading page looks like this:
The downloaded file is an installer. Its name on the PC is "Nav4_08_US_PPC.bin". After the copy to the Macintosh medium, the name (stored in the container) becomes "Nav4_08_US_PPC". This program creates a folder, named "Netscape Navigator_ 4.08" which contains the real installer.
Those steps should be noted in the readme file to inform the user.
Please also note that autostarting the installer should be considered as a really bad practice, since the majority of computer users already has some kind of browser installed.