I own V4 commercial and can purchase a V5 commercial upgrade from the original user, how easy is it to transfer the license? I own v6 as well.
The V5 commercial upgrade I intend to purchase from the 1st owner not a reseller/shop and was the upgrade from v4 commercial?
Why do you want to do this? An upgrade from V4 to V6 costs the same as an upgrade from V5 to V6.
Beware also, no matter what version is involved, if you are buying a license from a private party, you will need to fill out a license transfer form and have it signed by both parties and submit it to McNeel before the license can be validated. Also beware of people trying to sell you cracked or stolen licenses - best to verify the validity of the key with McNeel first before paying any money.