This was a small update released via Steam intended to fix specific technical bugs and improve the multiplayer experience. Key fixes in this and related "Silent Patch" versions included:
: Addressed issues such as infinite sprinting, scoreboard errors where team names were on the wrong side, and specific mission bugs like the inability to arrest targets in "Prison Break". Zero Hour Free Download (v9.1.5 Silent Patch 2)
If you are looking for a "free download," it is important to note that Zero Hour is a paid commercial game. This was a small update released via Steam