Uploading transcriptions of music described as Licensed and Royalty-Free

So I went to transcribe the main theme of an old childhood game after managing to find what the name of the song was, and ended up finishing it after a couple of [gruesome] sessions. I'd wish to upload it since it seems like a clean transcription and for the sake of nostalgia, but the part about selecting a copyright license got me confused.

When I went to search the specific song details, I encountered it in some common music streaming platforms as usual, but also in other sites that typically sell royalty-free licenses for its collection of music. I saw that collection to include a lot of songs by the original artist of the song in questions, including itself. I tried looking deeper to see what exact license category they fell under, but the information in that site was pretty vague for how usage works besides being able to buy a license for the original song.

With this, I'm now stuck with how uploading the transcription would work, as I'm quite unfamiliar with distinguishing the particular guidelines under each category, especially with however transcriptions are perceived. What license would such cases fall under, and would it be allowable to upload them here on MuseScore?

To be exact with the details, the song is Be Bop Polka by Skip Peck.