Startup script fails: "Could not find or load main class org.apache.vysper.spring.ServerMain"

In https://github.com/apache/mina-vysper/blob/685a690b3aa141f7ab9f275c8c29b0b043232dd4/README.md:

> A ready-to-run setup is created by the build in
>   `dist/target/appassembler/`
> Under
>   `dist/target/appassembler/bin`
> you'll find start scripts for Unix/Mac and Windows.

When I run `mvn install` and then try to run the startup script, here's the result:

> Error: Could not find or load main class org.apache.vysper.spring.ServerMain
> Caused by: java.lang.ClassNotFoundException: org.apache.vysper.spring.ServerMain

Indeed, I cannot find a class called `org.apache.vysper.spring.ServerMain` in the repository. There are several `ServerMain` classes but not one in package `org.apache.vysper.spring`.

Am I doing something wrong? Or is there an easy fix to get Vysper running?