To my eye (uneducated in Apple Motion), Apple Motion's Membrane looks like a direct copy/ripoff/whatever of the freebie Sinedots, especially Sinedots 2. You can get it here:
http://www.philipp-spoeth.de/aftereffects/sinedots.php
and here:
http://www.philipp-spoeth.de/aftereffects/sinedots2.php
This is early stuff from philipp-spoeth, who went on to do this:
http://www.frischluft.com/frischluft/index.php
Maybe he was involved in Membrane, or someone else had the same idea ("ripoff" above was a bit harsh, since I know nothing of the origins of membrane, but they looks alike to me).