As you may already have seen, the link to VMware's vCloud Director Evaluation (https://www.vmware.com/go/try-vcloud-director) just show the general product information page.
This might have to do with the fact that vCloud Director is a product exclusively for service providers, now. If you're a service provider, your aggregator should be able help you getting a trial key.
it's just an academic project , no service provider
I'm not sure if you'll get a key, then. Maybe one of VMware's employees who post here can help you.
Unfortunately not. We haven't provided trial keys in some time, since about 2013 when the sun started to set on the product for Enterprise customers.
If you happen to have a vCloud Suite 5.5 key, then I think that should work as well. But we don't generate trial keys for older versions of products, you would probably only be able to get a vCloud Suite 5.8 or 5.0 ... which won't work in vCloud Director, nor let you download it since its not part of the suite in that version.