No, not permanently. But it goes on sale for 90% off regularly.
The Extreme demo includes a large skirmish map with unlimited waves of enemies. It is not the full campaign, but it offers hours of free gameplay. Download it from Firefly’s official website. Download Game Stronghold Crusader Free Full Version
Let’s address the elephant in the room. Most websites offering a "free download" of Stronghold Crusader are either demos, shareware versions from 2002, or malicious traps. No, not permanently
While the temptation to via illegal means is understandable, the risks outweigh the benefits. For the price of a coffee, you can own the DRM-free HD edition on GOG.com, install it on unlimited computers, and play it forever without malware. shareware versions from 2002