Searching for a can be a bit like looking for a vintage engine in a modern dealership—you'll mostly find people trying to sell you the newest model or sketchy links you definitely shouldn't click. Rocscience is a heavyweight in geotechnical software, and their products are high-end commercial tools, not open-source freeware.
There is no permanent, full version of Rocscience Slide 6.0 available for free download legally. However, there are official ways to access Rocscience tools without an upfront purchase: rocscience slide 6.0 free download
Pirated versions lack: