KNX ETS4 4.2.3884.50021 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The software is included in Business Tools.
ETS4.exe, Ets4Icons.exe or ToolDiagWizard.exe are the common file names to indicate the KNX ETS4 installer. The following versions: 4.2, 4.1 and 4.0 were the most frequently downloaded ones by the program users. We recommend checking the downloaded files with any free antivirus. This tool was originally developed by KNX Association cvba. This PC program works fine with 32-bit versions of Windows XP/7/8.
From the developer:
ETS means Engineering Tool Software, a manufacturer independent configuration tool Software to design and configure intelligent home and building control installations with the KNX system.
The ETS focuses on all users of the KNX system, from the beginner up to the skilled and experienced KNX partner or installer.
You may want to check out more software, such as NETxKNX OPC Server - Direct KNX, ComBridge Studio Suite or ETS - InfoTerminal Touch Gira, which might be similar to KNX ETS4.