Since V4.3 is discontinued, the secure route is to obtain it through a valid license. Here are your options:

PC-based motion control running on a Windows real-time operating system expansion. P320-3, P350-3 5. System Requirements for Installation

Siemens typically provides a short-term trial period (often 14 to 21 days) for testing and evaluation purposes.

SIMOTION SCOUT 43 Download Guide: Overview, Compatibility, and Installation

Ensure Microsoft .NET Framework 3.5 and 4.0 are enabled on your operating system.

To ensure software integrity and avoid malware, always download automation software directly from official Siemens channels. The Siemens Industry Online Support (SIOS) Portal

Always run the setup file with administrative privileges to ensure all drivers for the communication cables (PC Adapter/CP cards) install correctly.

If the SIMOTION device is part of a machine, the original manufacturer may have a copy of the exact software version used for validation.

SIMOTION SCOUT 4.3 Link Download: Complete Guide to Motion Control Engineering

is the engineering framework for Siemens’ high-performance motion control system, SIMOTION. It is integrated into TIA Portal (for newer versions) or available as a standalone add-on to STEP 7. Version V4.3 (often referred to as "43" in informal searches) is a legacy release, widely used for maintaining older SIMOTION C, P, and D controllers.

Requires a pre-installed, compatible version of STEP 7 V5.5. SIMOTION SCOUT TIA