SBT (the simple built tool - popular in Scala circles), has been available to build with in DEV@cloud Jenkins some time.
You can use it directly on RUN@cloud as a convenience.
Read more about the stack:
How to use can be as simple as:
You specify in the args the "goals" for SBT to run.
When/why would you use this? Convenience. If you are building distros and running them as wars, or play dist, or jars then there is no need to change (you rarely would want to run clean/compile/run on each node, for example, but you could).