Well, it took longer than we thought, but we have SDI output in development versions; and it should be a quick hop to Beta. In the end, after going around and around with different SDI cards (there aren't many options on Linux, and what there was not that long ago was very expensive), our favorite supplier - Black Magic Design - brought out a full featured API that runs on Mac, Linux and Windows. Their range of cards, support and price points made it an easy decision.