They’re a paid service now. It’s no longer open source.

To the best of my knowledge Plex has never been open source. It's just easy to mix up because it's been using Kodi as a base the whole time.

	▲	oarsinsync 2 days ago \| parent [-]
		Indeed. They forked Xbox Media Center back in the day, to produce a Mac version when none existed. Then they became a client/server model. They are supposed to provide the source code for Plex Transcoder, since that's a modified ffmpeg build. In practice, the version they share is not up to date with the version they ship. They are generally speaking, closed source.