infernu VS Akka

Or maybe a sound type system can only be achieved either by limiting JavaScript or with a different language that compiles to JavaScript?

Very constrained. Since "constraints liberate, liberties constrain", as Bjarnason said. Inspired by Golang's minimalism, and Elm's guardrails. For learnability and maintainability. Since discipline doesn't scale (obligatory xkcd: with too much power, and the wrong nudges, all it takes is a moment of laziness/crunch-time to corrupt a strong foundation), and a complex language affords nerd-sniping kinds of puzzles, and bikeshedding and idiomatic analysis-paralysis. Counter-inspired by Haskell. The virtue of functional programming is that it subtracts features that are too-powerful/footguns (compared to OOP), namely: mutation & side-effects. The language designers should take care of and standardize all the idiomacy (natural modes of expression in the language). "Inside every big ugly language there is a small beautiful language trying to come out." -- sinelaw. The language should assume the developer is an unexperienced, lazy, (immediately) forgetful, and habitual creature. As long as software development is done by mere humans. This assumption sets the bar (the worst case), and is a good principle for DX, as well as UX. The constrained nature of the language should allow for quick learning and proficiency. Complexity should lie in the system and domain, not the language. When the language restricts what can be done, it's easier to understand what was done (a smaller space of possibilities reduces ambiguity and increases predictability, which gives speed for everyone, at a small initial learning cost). The language should avoid Pit of Despair programming, and leave the programmer in the Pit of Success: where its rules encourage you to write correct code in the first place. Inspired by Eric Lippert, but also by Rust.

Kotlin also has a construct for asynchronous collections/streams. Kotlin's version of AsyncSequence is called a Flow. Just as Swift's AsyncSequence builds upon prior experience with RxSwift and Combine, Kotlin's Flow APIs build upon earlier stream/collection APIs in the JVM ecosystem: Java's RxJava, Java8 Streams, Project Reactor, and Scala's Akka.

First-class distributed and multicore computing. Swift has first-class “actors” and “distributed” methods. Unison, Erlang, and Elixir are built with distributed being one of the #1 concerns. Though first-class is not super common and I don't really expect it to be because usually libraries are enough (e.g. Scala has Akka and is used WIDELY for distributed); whereas something like linear types and typed effects, you can't emulate in a library.

Akka is a library that implements the actor model for JVM languages. Mainly in Scala, but you can use it in Java too, and maybe others. It doesn't feel as ergonomic as Elixir, but if Elixir is too "out there" for the decision makers in your case, this might be a friendlier alternative.

Kalix builds on the lessons we have learned from more than a decade of building Akka (leveraging the actor model) and our experience helping large (and small) enterprises move to the cloud and use it in the most time, cost, and resource-efficient way possible.

Note Akka, the Java & friends framework, is working with the actor model and have as main inspiration Erlang to mimic some features of the BEAM on top of the JVM.

Looking back at real dates, I started learning the language (Scala) back in 2008 because it was something new and trendy that interested me. I started spending some serious time with it in 2009 (helping out other newcomers and making small contributions to various projects), and then in 2010 became a core contributor to the Akka project (you can find me a little ways down this list: https://github.com/akka/akka/graphs/contributors). For the most part I worked on the features I wanted to, but worked on other things if a user asked nicely. Akka became very popular in the early 2010s, so all of a sudden I had highly sought after skills. Got hired by a London based company and moved myself and my family from Canada over here. But even today, that exposure I got 10 years ago still helps me to land new contracts.

In the open source world, Akka, the most popular actor system library in the JVM ecosystem, that’s heavily used in tonnes of open source projects, recently went from “free and open source” to “paid/proprietary and source available.” https://github.com/akka/akka/pull/31561

Same strategy - the pricing is insanely high (for a library), and the project is effectively dead now, but it’ll take some larger enterprises awhile to move away from.

Lightbend, the company owning Akka, recently shared a blog post signed by the CEO announcing a license change from Apache 2.0 to Business Source License 1.1, a proprietary license. You can already find it in this PR, merged a couple days ago.

Akka 2.6 is on the open source Apache license, that is unchanged (its not possible for Lightbend to change an existing license). Its only the new Akka 2.7 which has the BSL license, so as long as you don't upgrade you are fine. See https://github.com/akka/akka/pull/31561.