How to stream from mac to a DLNA Renderer?
There are two free options you can try:


ffmpeg
VLC 


VLC offers a more friendly GUI interface though (IMO) it's much more limited.  ffmpeg is much more powerful, but it requires you to be command line savvy.

Personally, I prefer ffmpg.  They have a tutorial on how to stream point-to-point, which is what you are looking to do


  Point to point streaming
  
  If you want to stream "from one computer to another", you could start
  up a server on one, and then stream from FFmpeg to that server, then
  have the client connect to that server (server could either be on
  client or server side computers). Or you could do a point to point
  type stream, like:

ffmpeg -i INPUT -acodec libmp3lame -ar 11025 --f rtp rtp://host:port

  
  where host is the receiving IP. Then receive the stream using VLC or
  ffmpeg from that port (since rtp uses UDP, the receiver can start up
  any time).
  
  or

ffmpeg -i INPUT -f mpegts udp://host:port