Do I need to get a new license when I buy a new laptop? I want to get Lightroom, but I'm also thinking about changing from Windows to Mac.
No, you can simply download Lightroom for you Mac, install it an use it. Keeping Lightroom Up-to-Date
If your Windows computer is running Lightroom 6 or Lightroom CC 2015, you want to de-activate Lightroom on the Windows computer using the Sign Out menu command.
Your license is good for both platforms. You will need your serial number in order to install on your new Mac. Here are some good instructions on what to consider when moving Lightroom to a new computer:
thanks! That's what I needed to know!