While there is no permanent free version, Bohemia Interactive occasionally hosts Free Weekends on Steam, allowing players to download and play the full game for a limited time. Highlights of Update v0.9.5.109
If you are specifically looking for version 0.9.5.109, it was a milestone patch that significantly expanded the game's multiplayer capabilities: Arma Reforger Free Downlaod (v0.9.5.109)
Addressed various crashes (e.g., building mode, ladder usage) and tweaked vehicle interactions, such as fixing the Ural truck's trunk actions. How to Get it Safely Arma Reforger on Steam While there is no permanent free version, Bohemia
Enabled PC and Xbox players to join the same servers for the first time. ladder usage) and tweaked vehicle interactions