I have just purchased another two WTOS S10’s they are still in the box and I wanted to put the latest firmware, which they should have on them onto the ftp server so that everythnig updates to the latest.
Latest firmware can only be purchased via Wyse.
For a limited time after you bought new units you are allowed to get the latest FW for free from Wyse Support but after that time (not sure if it is 90 days more or less) you would have to buy an upgrade.
If you have older units and buy 2 new ones, you can only upgrade the new 2 units but not all. Otherwise you are violating a license agreement.
Best would be, and I always recommend this, to buy WTOS maintenance. After that you can upgrade at any time for free.