Cross-platform license

My activation code works fine on my computer Ubuntu but fails on the same machine if I boot into Windows 8.  Is the activation code restricted to an operating system?  Would I lose it's use if I upgraded Ubuntu at some point? 

You should be able to use your license with different operating system, as long as it is the same computer, but sometimes this doesn't work properly. Please fill a support ticket with your computer and operating system details, in order to solve this issue.