Upgrade possible between versions?

Initially I was interested in the Lite version of FD but I was wondering whether there was a possibility of an upgrade to the Workstation version if I found that it better suited my needs.

However, after sending an email to Leapfrog they sent back a reply saying that there was no upgrade path from the Lite product.

If this is the case, why is there an upgrade option within the Lite trial product?

Is this simply to convert the trial to a fully licensed copy or is there in fact an upgrade option to the Workstation version? (Incidentally the upgrade button does not work).