For each Jamboard you buy, you need one management license.
You can buy a license annually — either directly from Google or your reseller. Licenses cost USD 600 per year. There is a special promotion until September 30, 2017, where Jamboard licenses are discounted 50% from the MSRP and cost USD 300 for the first year.
If you have more than one Jamboard in your domain, you can transfer licenses are transferrable among them. If you return one board, you can use an existing license in your domain for the new board you receive.
If you have a damaged board or one that you’re returning, remove the setup for your board.
Note: You don't need Jamboard licenses to download and use the phone or tablet apps or web viewer for Jamboard. You also don't need licenses per user for the apps. The licenses are specific to the board.