Jeff from PipelineDB here. Our products are similar in that they execute SQL queries continuously on streaming data, but the main differences are that PipelineDB is 1) open-source, and 2) includes a fully functional relational database, which enables "state" and doesn't presume that data is intended to be streamed out as well as in. The latter is a seemingly subtle, but important difference because "stream out only" drastically limits use cases.