As a piece of software history, the original European and North American versions are hosted on the Internet Archive for free historical browsing and download.
Some retro gaming sites like RetroOnline offer the ability to play the game directly in a web browser, though performance can vary based on your system's memory. Meet Your Elite Squad Save 50% on Commandos: Behind Enemy Lines on Steam Commandos Behind Enemy Lines Full Game Free
For those who want a taste of the gameplay before committing, a free demo remains available via Archive.org. As a piece of software history, the original