It is a common point of confusion, but the "20" in your search term does not typically refer to a "20 key." In the context of this specific legacy software, "20" usually refers to the AirBrush "20%" setting (a specific smoothing algorithm) or simply the version numbering (v2.0).
When the software was released, it was typically distributed as a fully functional trial version. Users could download the plug-in for Adobe Photoshop and test it on their photos, but the output would have a prominent digital watermark across the center. kodak digital gem airbrush professional 20 key
You can recreate 80% of the effect using native PS tools: It is a common point of confusion, but
Performance: The plug-in can use up to 6.66x the image size in memory during processing. Low Radius: Protects small details (pores, eyelashes)