Launcher is a program one can use to run virtual job arrays.  I call it a virtual job array because the scheduler sees your Launcher job as a single job, but inside that single job Launcher behaves like a traditional job array from Slurm or Moab.  This software can be used to get around various limits placed on users by the admins of a cluster.  It is not necessarily malicious because technically a job you submit using launcher will adhere to the rules of the cluster; it has to in order to run.

Launcher might have features that the cluster's scheduler does not natively support, or features that may have been disabled by the admins of the cluster.  One can also use Launcher to make their HPC workflow portable.  If one designs their workflow around Launcher, they will only have to change a few environment variables to port their jobs to different clusters with different schedulers and different rules.  Launcher also mostly removes the need to learn how the scheduler works.  The researcher just has to know how Launcher works, and Launcher acts as a compatibility layer between the researcher's workflow and the cluster it is running on.