Those contributors contributed when it was not under the Apache license. They either need to get all rights assigned to them (DataStax) and then they can relice

Those contributors contributed when it was not under the Apache license. They either need to get all rights assigned to them (DataStax) and then they can relicense it under Apache, or they need to get all contributors to agree to relicense under Apache. Looks like they are taking option 1 because it will make relicensing less of a headache in the future if it becomes necessary.