By purchasing SongKong you get:
Many of us have multiple computers these days so SongKong can be used by one person on upto three computers, and the license is not tied to PC or Mac only - you can use the same license on both. However the regular SongKong license is intended for personal use only, if you are organising multiple music libraries on behalf of others or you are using SongKong within a business setting you need to purchase the SongKong Commercial license.
Pro, Melco and Commercial offer additional features over the Standard version, full details here
If purchasing a Pro Upgrade using Paypal the license will be sent to your registered Paypal email address, please ensure this is the same address as your license is registered to otherwise the new license will not work.