While "cracked" versions of the retail game exist on various third-party sites, you can legally play a free, standalone version of Black Mesa
Black Mesa (originally Black Mesa: Source) began in 2004 as a response to the underwhelming Half-Life: Source port. Two mod teams merged to form Crowbar Collective, aiming to rebuild the original game from the ground up using the then-new Source Engine. black mesa source non steam crack only top
How to Install Black Mesa (Source Mod) - Presented by Mr. Odd 15 Sept 2012 — While "cracked" versions of the retail game exist
Wait for Sales: Black Mesa is frequently discounted by 75% or more during Steam seasonal sales, often dropping to the price of a cup of coffee. you can legally play a free
Finding a Non-Steam Crack for Black Mesa Source