http://lainyubrp2aabmxhepbttfdbl53dct2inqifs42buvpf6w44uiitbeqd.onion/blog/matrix.html
It's a main funding source, a for-profit organization, so they can afford making average quality software. And yes, of course there are server implementations and clients from individuals here. ...But they are fully imbued with the very spirit of open-source.