Describe yourself:
"I'll never let go of my Squeezebox and/or enjoy living in the past and/or need it to run on Windows" https://github.com/Logitech/slimserver
"I'm a sysadmin with a Roku SoundBridge" https://en.m.wikipedia.org/wiki/Firefly_Media_Server is another, specifically for Roku Soundbridge and iTunes streaming protocols.
"I'm running FreeNAS and just want to use a plugin" Subsonic is another http://www.subsonic.org/pages/index.jsp . Can also do Shoutcast streaming.
"I know what RMAF stands for and/or like messing with SBCs and/or spending $10k on audio equipment" http://www.runeaudio.com
"I run Arch with a tiling wm" Lastly are the mpd family of servers and clients. These are for the hardcore nerds who love recompiling ffmpeg from source. Servers: https://www.musicpd.org // https://www.mopidy.com
Clients: https://www.musicpd.org/clients/ // https://docs.mopidy.com/en/latest/clients/mpd/ // http://www.runeaudio.com/clients/
It's totally open source, has a relatively decent web player, allows you to stream your music anywhere, allows you to create accounts for others to have access to your music, can connect with Plex/subsonic to work with other devices/clients. I use DSub on my phone, and can sync music offline (like GPlay Music). Only downsides really is that it requires a web server and the initial import can take some time if your library is very large.