The 2400 controller is capable of running ArubaOS version 5.x. It's not capable of running version 6.
Firmware upgrades are available for download from the Aruba support website. Without a valid support contract, I'm not sure you'll be able to get access to the site.
As for eval licenses, they are available from the licensing website. Again, without a support contract, your access to that site may be limited.
Your best bet is to discuss this with your SE. He or she may be able to get you the info and access you need.
Hope this helps.
- Jay