You can use http://srecorder.com/ you just need to set your system default audio recording device by right clicking on your speaker icon and record in real time. Unlike WinBB it saves to a small mp4 rather than a large avi

Also http://camstudio.org/

On the Mac you can use Quicktime player File > New Screen Recording in the drop down select Soundflower 2ch and in System Prefs - Sound, set Output to Soundflower 2ch https://www.macupdate.com/app/mac/14067/soundflower# or search the many free ones.

To post on the forum upload your video to a free dropbox or file storage site.

This is neat.
Saves me from using a Video converter.

DE

Another one is https://sourceforge.net/projects/screenrecorder-x/

This seems like the best so far:
Win/Mac Free Video Screen Capture Software Active Presenter
Though, BB18 might have Notation to Video.