Here's the quote, right off of the Pass Bureau website...

"Travel companions and nondependent children – Travel companions and nondependent children are eligible for unlimited S3B yield fare tickets on Delta and Comair domestic and international flights. The purchase of a space-available yield fare ticket is required. Travel on Delta’s other DCI partners that operate flights as Delta Connection flights (except for American Eagle) will be at the S3CR boarding priority. (Yield fare ticket required)"