First, Spectrasonics does not sell licenses via Valve. Therefore, any website offering a "Steam unlocked" or "Steam folder" version of Keyscape is lying to you. They are using the term "Steam" as clickbait to make you think the download is safe and easy (like a drag-and-drop game crack).
Inside the main STEAM folder, there should be an "Omnisphere" folder. You need to place your "Keyscape" library folder right next to it. keyscape steam folder download reddit
Ensure the file sizes match between the original and the copy before deleting the original. First, Spectrasonics does not sell licenses via Valve