This option has always existed since it's used by FifoCI, but now it can be changed at runtime. Looping is something that should almost always be on, but it can be useful to turn it off when frame-dumping is enabled so that hundreds of copies of the same frame aren't created. Before, turning it off required restarting Dolphin.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
This way, it can be focused with the render window behind it, instead of having the main window show up and cover the render window. This is useful for adjusting the object range, among other things.