Can I use Red5 Pro for screen sharing?
We recommend trying JUV RTMP Client. There are many ways you can deploy this. You could package up as an Applet to be delivered over the web as well. There may be caveats… like it doesn’t work with this specific version of the browser or that the end user must have a version of Java installed (applet requirement), but these are usually mitigated through proper direction to your end users. You can request an evaluation key from that site.
Another option is "Open Broadcaster Software"