The main difference between current score implementation is that score equation needs only time as an input, but proper implementation of DGM need to know also count of already submitted shares (across all backends). Pool core is designed quite scalable, there's no online synchronization between backends necessary, but it goes against DGM requirements. And it's the pain and the reason why it takes so much time. Originally I expect that it won't be so hard, but I felt into solving strange threading issues (cause framework which I'm currently using doesn't natively support user's threads).