Didn't they remove the key requirement in 3.9 anyhow? I managed to buy an MUI key way way back when. Still have it and MagicWB versions I paid for on my hard drive.
But I would think by now that MUI should just be open sourced, since it's such a required library for the Amiga.
slaapliedje
P.S. That of course doesn't mean they shouldn't receive donations for putting out new versions.