The best open source alternative to CloudStream is Taiga. If that doesn't suit you, our users have ranked more than 50 alternatives to CloudStream and 14 is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to CloudStream are DuckieTV (Free, Open Source), Aniyomi (Free, Open Source), popcorn-time.to (Free, Open Source) and TeaTV (Free, Open Source).
Oblecto is a media server, similar to Plex, Emby, Netflix and others. It runs in the background on a home server to index your media such as movies and TV shows to make them searchable and streamable through a REST based interface.