I am not a Java Developer, but I would think this is not much more than changing a label to a textbox and writing the content of the textbox instead of the string comming from the server to the database.
According to my experience, even the craziest CalDAV/XML/HTTP problems are nothing compared to GUI tasks like creating a text field (and: making it actually editable, the cursor not disappear, scrollable, not crashing when the screen is being rotated and or a TV is attached; it should also retain the contents when the users switches to another activity and then back; and of course it must work on 24" TV screen as well as on wearables………). OK, maybe somehow over-exaggerated, but I want to say that even a simple GUI change is lot of work and may cause lots of trouble.
But the main reason for not implementing this is that the server already provides a “display name” for the calendar. If you want to change the displayed name of the calendar (= display name), you have to make the server providing the correct display name.
No, unfortunately I have no access to these settings.
Who has access to these settings? Would your administrator be able to rename the calendars?