Do I need to "unregister" an OSX virtual machine? I have an OSX VM (using VMWare fusion 6), and want to delete it.

VMWare's docs say "Apple's updated license agreement allows you to install up to two additional copies of Lion on your Mac which is already running a retail version of Lion"

I remember something in the installation, possibly linking to my Apple ID saying that I could only install 1-2 copies in a VM too (I installed Mavericks, 10.9)

If I'm going to delete this VM, and want to create other OSX VMs in the future, can I/do I need to "unregister" this VM?
There's no registration for OS X, and nothing in the code to detect and prevent you running more than two VMs. It's purely a legal restriction. If you've deleted the VM, then you're fine.