The OpenLDV 5.0 driver is available from http://www.echelon.com/software-downloads?ele=153-0411-01B
I just tried to download it now, and it is working.
Did you fill in the information and click Download? Then, you should get a pop-up Window with an Accept button.
If you are still having problems, maybe try to add www.echelon.com in your trusted web sites, or maybe try a different browser.
If you continue to have issues, please contact us at www.echelon.com/support