Dieseldick uses a Kodi box but there won't be much point in us directing him to this post (whenever he's next around) unless you ask a specific question about Kodi devices.
While Kodi itself is legal, the use of 'fully loaded' Kodi devices, to obtain subscription services without payment, almost certainly isn't. There are cases currently before the courts, where people selling 'fully loaded' Kodi boxes are being prosecuted and it's likely that the Federation Against Copyright Theft (and/or rights owners, such as BSkyB) will eventually also take legal action against people who use such devices.