There is no standalone "demo" or separate installer for Keylight 1.2 for CS5 that functions without the host program. Because it was a bundled, licensed plugin, it is tied to the installation of the Adobe Creative Suite itself.
In the early days of After Effects (versions prior to CS5), keying was often a struggle. Users relied on the built-in "Keylight" (which was often a stripped-down version) or third-party plugins like Primatte or Ultimatte. However, with the release of , a monumental shift occurred. --- After Effects Cs5 Plugin Keylight 1.2 Download
Run the Adobe Help > Updates tool. The 10.0.2 or 10.5 updates often re-link broken paths for bundled plugins like Keylight and Mocha. There is no standalone "demo" or separate installer
