Re-claiming iWork App Licenses

When you purchase your devices, you can apply to Apple to get managed licensed for all the devices, iOS and OSX

This is located on the Contact Support link in the VPP Purchasing account:
To request free iLife and iWork apps for qualifying Mac or iOS devices through the Volume Purchase Program:

Visit the vpp-fulfill.apple.com support site.

But what if I have already purchased a set of iPads with Numbers, iMovie, Pages, Keynote, and GarageBand already installed on them and I don't need those particular apps on that class set of iPads? How can I get those apps/licenses moved to a class set where I can use the apps?

Once you have the managed licenses you can deploy them to any devices, using App Distribution from your MDM

I understand about Managed licenses and distributing them with my MDM (JSS in this case.)

What I'm asking is when I purchase a new iPad that already has the iWorks suite on it how can I claim those licenses from that iPad, get them into my Mobile Device Apps pool, and use them on another iPad that might be older and not have the Suite?

You do not need to reclaim them from the existing devices. If the first user on a device claimed the apps in their Apple ID, they are theirs to keep forever.

Apple will give you a set of licenses (iLife and iWork) for every purchased device wen you request them.
They show up in your VPP and then in your MDM, where you can distribute them where ever you want.

Our iPads are in our DEP and are Supervised...none of them are logged into an Apple ID. We deploy the apps to device, not Apple ID.

@pshouston as @Sandy mentioned, you can request VPP codes from Apple for all equipment you purchased from Apple. You just need to visit their fulfillment site:

VPP Fulfilment

You will need to be able to provide a list of serial numbers and proof of purchase. Once approved, Apple will update your VPP account with the necessary licenses/codes. You can then deploy as you see fit.