Mac CD and Linux

[Ed Martin]

Hi,
I have a Mac and a Linux box, and i would like to have a mobile install
of UT3 (Mac), plus one on my desktop (Linux)

So my questions are will it be possible to install on a Mac with the
Windows CD (i would like to preorder on Amazon but i don't see anywhere
to preorder the Mac CD), and if not would it be possible to install on
Linux with the Mac CD, basically i would like to only get one key but
have it installed on Linux and Mac (as i would only ever play on one
system or the other, never both at the same time). If I have to i have
no problem buying the two keys.