"4. Can I simulcast?"
"You cannot simulcast Facebook lives to any third-party sites. The only exception is if you are an owner of a website and are broadcasting to your Facebook page and would like to broadcast to your own first-party site. For example, if you are a sports team and want to stream to Facebook and to your athletics page, that is an acceptable instance of simulcasting. Please review our Live Video policies to ensure your streams are in compliance."
"You can go live on YouTube, or go live on Facebook, but not both."
"Due to a newly enforced Facebook Platform Policy, you must choose to either simulcast to Facebook or simulcast to other live streaming services such as YouTube, Periscope, or any Custom RTMP Destination of your choice. You may still stream simultaneously to multiple Facebook Pages and to your website."
"Facebook prohibits companies from using its Live API to enable others to broadcast live videos to its social network and third-party sites at the same time. In other words, a company like Vimeo is forbidden from enabling creators to simultaneously broadcast to Facebook and YouTube or Facebook and Periscope or Facebook and Twitch. So it’s not actually enabling that, even though its announcement claims that creators “can now simultaneously live stream to Facebook, YouTube, Twitch, Periscope, and more — along with wherever you embed the Vimeo player.”
"According to a Vimeo spokesperson, creators will not be able to use Vimeo’s simulcasting feature to simultaneously broadcast to Facebook and YouTube, Twitch or Periscope. Instead, they will only be able to simulcast to Facebook and Vimeo (but not YouTube, Twitch or Periscope) or to YouTube, Twitch, Periscope and Vimeo (but not Facebook)."
"Simulcasting to Facebook and Vimeo appears to be OK because of an exception Facebook makes for a company using its Live API to stream live to Facebook and the company’s own site simultaneously. “The only exception [to Facebook’s policy against third-party simulcasting] is if you are an owner of a website and are broadcasting to your Facebook page and would like to broadcast to your own first-party site,” according to an FAQ section on Facebook’s developers site."