Opensourcing sounds good. The problem is the right license choice. If they use something like Apache/LGPL "business friendly" license then soon or later Amazon will take the product, pack it into its cloud offering and Datomic will get nothing (MongoDB case). Maybe dual license GPL 3 or AGPL plus commercial would work, the question is how it would affect their business. Maybe if they are doing well with current model there is not incentive to change anything.