To change login screens you need a modified exe to change the images as well as size and position of every button etc. Yet this does in no way affect the ingame experience so it shouldn't be bannable imo.
4th sentence:
All you need to do is run application + select login screen background/music and hit Apply button.
Without actually being able to see the file we can only go by that^ Since it's an application I would assume no, but the fact that it literally does nothing apart from change your login screen means that it MAY be allowed.
If you do, or already have, downloaded it I would advise NOT to use it until a member of staff gives you the thumbs up for it.
To change login screens you need a modified exe to change the images as well as size and position of every button etc. Yet this does in no way affect the ingame experience so it shouldn't be bannable imo.
Should or shouldn't doesn't matter.
It's a modified client, that may be picked as hacking. I don't know a lot about how warmane's anti-cheat works except that it doesn't like people tampering with wow.exe. Be it modding for malicious purposes or for adding ponies instead of horses, I highly doubt it can tell the difference.