Digital Eclipse said several times their game is based on the original code, so Sir-Tech would need Greenberg's consent. If he doesn't know about it, either he settled with Sir-Tech and cancelled the agreement
I'm sure they have settled a long time ago. He'd have to be a total lunatic to still hold a grudge against a long defunct company in the industry he has long left behind him after all these years.
You really think Sirotek would just greenlight it after Greenberg litigated with him for 10 years and drove his company to the ground? "Pah, it's probably nothing, he'll never find out?" Nigga, please.