1. We want a venue in which we can rapidly iterate and make new releases. The overhead of making a release as a separate project is minuscule (in the order of minutes). A release on Spark takes a lot longer (in the order of days)

2. Koalas takes a different approach that might contradict Spark’s API design principles, and those principles cannot be changed lightly given the large user base of Spark. A new, separate project provides an opportunity for us to experiment with new design principles.