What is 'akka.home' configuration?

In akka there is akka.home property is configuration, what is it used for?

 val EnvHome = System.getenv("AKKA_HOME") match {
    case null | "" | "." ⇒ None
    case value           ⇒ Some(value)
  }

  val SystemHome = System.getProperty("akka.home") match {
    case null | "" ⇒ None
    case value     ⇒ Some(value)
  }

  val GlobalHome = SystemHome orElse EnvHome

If I check akka source code it looks like it is no longer in use, is it legacy?

Regards,
Kyrylo

I think it was related to the “micro kernel” (https://doc.akka.io/docs/akka/2.3/scala/microkernel.html). It was there in Akka 2.2, deprecated in 2.3 and removed in 2.4.