So I was watching an LGR Blerbs video he did recently which covers this exact topic namely repackaged, sold for small profit margins physical discs of the shareware version of games such as Keen. I suspect that is what this disc is, too. These were sold in relatively above-board locations such as convenience stores. I doubt they would have usually distributed full version titles like Keen 5. I suspect this disc would have contained Keen4 only. I mean look at the art, it's all Keen4 stuff. They may have even deliberately left it vague knowing that kids (who maybe already had Keen4) might hope to get lucky.
Do check out the LGR Blurbs video, as it shows another
knock off Keen disc cover which is quite amusing in its simultaneous effort and lack of effort.
You'll see what I mean; the keen disc is first seen around 1:20 in the vid.