That's my understanding. The title screen acknowledges the debt for the "look and feel," which they licensed from Origin. I haven't heard of any attempt to get by, and that seems confirmed by SSI's few CRPGs after their break from TSR, which certainly weren't rip-offs of AD&D. You did have people like Edu-Ware getting sued by the tabletop game they ripped off (GDW's Traveller). TSR seems to have been oddly lax in letting so much get by that was obviously based on AD&D, such as the spell names and basic character classes. Of course, SSI did come pretty close to ripping Tolkien a few times, and countless games that started off with "hobbits" changed it to "halfling" or some other name.

It is strange how these obvious clones didn't arouse any ire from Origin or SSI, though. Seems hard to imagine they simply didn't know about them. Maybe they just thought going to court wasn't worth it for that sales volume (I really don't know).