In the heat of the moment, this setup seems to be a bit misleading :D at first glance, I thought I could buy the Companion right here and now (yeah, I know, one should properly read everything of course ^^). But that's also a known problem on itch.io, sometimes it's not easily visible that you own something already, even on the check-out page, it doesn't tell you.
(it won't let me attach a screenshot, but it's not really necessary, since everybody can see the "Buy" button right below the cover)