<< How do you import Moi's geometry? I can't find a way to do that.

It's a little tricky! ;)

Draw anything with Moi
Export as Image :
you can use the Button Print screen and past the clipboard in your 2D favorite program
or the script http://kyticka.webzdarma.cz/3d/moi/#CaptureViewToClipboard

In your 2D Prog save as format PNG (with background transparent)

In Algodoo draw a surface rectangle or anything you want with this image as texture
Convert this Texture in Polygon! ;)

As you can see Algoodo can use volume, surfaces or curves as 2D polygons! (of course in 2D )