This is one of the installs listed for ArcGIS 10.4.1. I already have database server connections set up in Catalog. Is there a reason I should install this?
Existing ArcGIS for Desktop users—Help | ArcGIS for Desktop says yes for license manager but remains silent (probably meaning yes) for the others.
I think you are looking at this.... Database servers—Help | ArcGIS for Desktop
This is a completely separate product that is not required to use ArcGIS for Desktop. I would not use it unless needed, too many limitations in my opinion.
Here is more details on database servers: Types of geodatabases—ArcGIS Help | ArcGIS for Desktop - Look at the section - How is ArcSDE technology included in ArcGIS?
Hope this helps!
Database Server for Desktop is the new name for "ArcSDE Personal". It comes free with ArcGIS Desktop.
The link that George provided should give you more details.