The Claris software license agreement stipulates that you may not donate, sell, or transfer the old version of your software after purchasing an upgrade. Although the new version may come with a new serial number, the owner still only has one software license.
The exact legal specifics from the Software License agreement read:
1.License
(d) Notwithstanding any other terms in this License, if the Software is licensed as an Upgrade or Update, then you may only use the Software to replace previously validly licensed versions of the same software. You agree that the upgrade or update does not constitute the granting of a second license to the Software (i.e., you may not use the upgrade or update in addition to the software it is replacing, nor may you transfer the software which is replaced to a third party).