use parallels desktop, vmware, wine, crossover or whatever

1 - when you launch mathematica click on the other ways to activate button along the bottom left of the window
2 - click on offline activation
3 - copy the mathid you see at the end of the mathematica window's step 1 text into the keygen
4 - paste the mathid into the top box in the keygen and click the generate button
5 - copy the activation text from the left box in the keygen into the activation field in mathematica
5 - copy the password text from the right box in the keygen into the password field in mathematica
6 - click on the activate button in mathematica.
7 - if something goes wrong, repeat 1-6 steps until it's done