I got the key I needed yesterday through my gmail archive where I found an older response from the system that had all the keys shown. I was trying to get the ODNT subscriber discount for CursorFX Plus while placing the order on a laptop that didn't have Impulse installed. So I used the web page form Neil linked then to get the ODNT serial...but the keys weren't in the email response. Later, I moved to a system where I did have Impulse installed, and used the Impulse Client request - which Neil correctly points out doesn't work atm.
Neil, I tried that web form again at https://www.stardock.com/support/ after you posted and it has *some* keys shown in the response email. Best I can tell, it only shows keys for Stardock developed products (e.g., ODNT stuff), plus Sins of a Solar Empire and Demigod (which are special cases, given the close ties between SD and those development teams).
But the email from the form on https://www.stardock.com/support/ does not have keys for any non-Stardock games, e.g., Civ 3, SupCom, The Witcher, Railroads!, and whatever else I've collected. There is something wrong, because in that older email I had, there were definitely keys for those games, esp. The Witcher, which had two keys (one for the game, one of the CDProjekt Red website extras that weren't part of the original Stardock The Witcher download package).
This issue isn't critical to me now, as I mentioned I got the key, but something is wrong with the responder at https://www.stardock.com/support/ as well, since you (or I) only get Stardock product keys through that service.