And now they have refused to release the code to ED, who apparently were willing to continue development of the Hawk. So anyone who bought after Oct 2018 can get a refund, for everyone else you need to stay on an old version to continue using it.
"DCS: BAE Hawk Update We regret to inform you that VEAO is no longer a developer for DCS World. As such, they have also ceased support of their Hawk. Although we offered to support their product, they declined making the files available to do so.
Given this unfortunate situation, we will fully refund all Hawk customers that purchased the module starting from 1 October 2018. If you wish a full refund, please enter a support request here.
For those that purchased the Hawk prior to 1 October 2018, will continue to make DCS World 2.5.3 available, such that you can still fly the Hawk.
To avoid such issues in the future, all future 3rd party agreements are now required to make the game files available in case they are no longer able to support their product."