Technically, the Interface Checker itself is often distributed freely within the enthusiast community. The "cracked" terminology usually refers to two things:
Some versions are modified to allow users to "flash" their hardware to version 4.4.0 (or higher) even if the hardware was originally restricted. The Risks of Using Cracked Diagnostic Software
Never install cracked automotive software on a computer containing personal or financial information. Use an old "shop laptop" with no internet connection.
Official PSA tools are locked to authorized hardware. Cracked versions allow "clone" interfaces (cheaper hardware from third-party manufacturers) to be recognized as genuine.
Files found on "free" forums or file-sharing sites often contain trojans or keyloggers designed to infect the laptop you use for car diagnostics.
Run the Interface Checker to see if your VCI is "Reference B" or "Reference C." Most Diagbox versions above 7.02 require Reference C .