C-Labs EULA has these three easy rules:

• You purchase one product of one major version and you can download any update to this version for free (i.e. you purchase Version 3.5 you can download all 3.x versions)
• You can install ONE product on ONE device at a time. If you decide to move to a different device you have to uninstall from the former device and than install it on the other device. You can switch between device types at anytime at no cost (i.e. you can start with the PC version and than move to a Pocket PC. You have to uninstall the PC version first than install the Pocket PC version).
• If you want to run any product on multiple devices at the same time, you have to purchase a license for each of your devices.

Very simple - isn't it?