Complex sentence: Netscape Navigator 2 was a proprietary web browser released by Netscape Communications Corporation as its flagship product for Microsoft Windows, but initially with versions available for Apple Macintosh, Sun Solaris, and HP-UX.
Split into simpler sentences: Netscape Navigator 2 was a proprietary web browser released by Netscape Communications Corporation as its flagship product. Versions were available for Microsoft Windows, Apple Macintosh, Sun Solaris, and HP-UX.