I was helping a clinical researcher to set up 4.10 on mac, and I ran into the message below. Installing XCode is a long step that I would not expect to be required to use Slicer. I don’t think XCode was required in the past.
Apparently, we were able to proceed with “Not Now”, but it is not clear what (if any) functionality of Slicer would not be available due to this.
There is no mention of XCode requirements in the install instructions here: New users - Slicer Wiki