I have a brother and we are both paying for the game. I'm on a macbook and he's on vista. Do you need the disc inserted at all times to play it? Then we could both play it.
The DRM with Spore is different than others. You don't require the CD to play (in fact you can read this on the spore website) but your limited to 3 installations. Beyond 3, you need to contact them and get the count extended.
You don't need the disc for mac or pc after installation and uninstalling doesn't give you it back, also if you upgrade your operating system, that counts for one, but I'm not sure how that would work.
There's nothing that states a pay for reinstall where are you getting that?
You bought the game and do not need to pay anything else, but if you install it and reinstall it enough times (3 is the limit) then you have to contact them to verify that YOU need the additional installs and no one else.