Référentiel libreelec
LibreELEC is a fork which means they took the OpenELEC code and used it as a starting point for their own project. So to answer your question, it is mostly identical as far as the end-user is concerned. A key difference right now is that LibreELEC is active and up to date. OpenELEC had no development for several months. I see some development activity lately but with no announcements from the