In 2022 Lightbend relicensed Akka from Apache 2.0 to BSL, which was a huge problem for all of the other opensource projects (like Flink) that used it as part of their coordination layer. At this point most or all of them have moved to Pekko, which is a fork of the last release of Akka under Apache 2.0.
An important design consideration for Hydro, it seems, is to be able to define a workflow in a higher level language and then be able to cut them into different binaries.
Is that something Akka / RX offer? My quick thought is that they structure code in one binary.