It adds an entry to your firewall when the program starts, allowing you to access ETS2 Local Radio (so yourip:8330), and it consequently removes that entry again when the program exits. That requires administrator rights.
It copies the plugin to your ETS2/ATS installation folder, and depending on where that is located, that requires administrator rights.
Similar programs, such as ETS2 Telemetry Server, also require admin rights (only they make a permanent firewall entry, so they only request it at first start).
(There may be a couple of other things I have forgotten that need administrator rights, but you can probably see that there is a reason for it.)
You can check the source code on https://github.com/Koenvh1/ets2-local-radio, and for the individual dependencies on their respective websites:
- https://github.com/gmamaladze/globalmousekeyhook
- https://github.com/JamesNK/Newtonsoft.Json
- https://github.com/SlimDX/slimdx
- https://github.com/vvvv/SVG
- https://github.com/EasyHook/EasyHook
- https://github.com/sharpdx/SharpDX
Should give you some nice bedtime reading

@joschac2 Try https://github.com/Koenvh1/ets2-local-r ... emetry.dll
@ThunderSky Make a station a favourite, and it will always start playing that station when you enter a country (or region)