Since this is an older version, it is no longer featured on the primary Oracle SQL Developer Downloads page. You can typically find it through the following official channels:

Operating System: Windows 7, 8, or Windows Server 2008 (also runs on newer versions in compatibility mode).

Windows 32/64-bit: Requires you to have a JDK already installed. Mac OSX/Linux: Provided as a ZIP or RPM file. System Requirements and Installation