sorry, but i do not understand what exactly you are trying to do here

users have id’s which are referenced in the wppizza orders table (and pretty much throughout your whole wordpress installation) and have meta information added if necessary

if you also want to delete all categories and items then you are simply adding some users to wordpress (wppizza does not create it’s own userbase but simply uses the users registered in wordpress and allows for registration to those users)

that said, if you just want to move an installation somewhere, there are plenty of cloning plugins that would let you do that

generally speaking though, partially removing or copying things might cause you all sorts of problems as id numbers might change (but it really depends)

(i also don’t really understand what this has to do with licenses of things)

you can clone and then change things afterwards as you like
that isn’t really a wppizza issue or question though but simply how to administer wordpress sites in general

i would say clone away, empty order table (or delete orders one by one) and delete the users as you like, but all at your own risk