I want to use Boxcryptor Portable from a USB device and I only need a free account. On the pricing page it says free accounts can use 2 devices. Does this mean I can only use the Boxcryptor Portable from the USB on 2 different computers?
this is right, you can use it on 2 different computers at the same time.
But don't worry, if there is a computer you don't use anymore you can unlink the device and add a new one.
A short addition from my side: If you ensure to always sign out after you completed your work on a computer, everything should be fine. If you forget to sign out on a computer, you can always unlink old computers from your account https://www.boxcryptor.com/app