Unless you are specifically maintaining a 15-year-old machine that cannot be upgraded and requires a specific legacy driver, do not download V4.0. The security risks and compatibility headaches are not worth the "free" price tag. Download the official modern demo version from PTC/Kepware instead—it is safer, faster, and legally free to use for testing. Libronix Digital Library
V4.0 was designed for an era before modern cybersecurity standards (like IEC 62443) became mandatory. It lacks modern encryption, user authentication protocols, and security patches found in V6.0+. Connecting a V4.0 instance to a modern network creates a significant security liability. Days Gone Fitgirl Repack Days Gone Highly C Better
Verdict: A Legacy Industrial Workhorse, But Obsolete by Modern Standards.