Play using the source for Blender (so you will need Blender to play):
http://code.google.com/p/manuel-bellersen/downloads/detail?name=NotAlone_Out.blend

You can get Blender from here:
http://www.blender.org/download/get-blender/

or svn versions from here:
http://graphicall.org/blender

(You don't need to install Blender. Just grab the zip, extract it, and start Blender.
I will try to put on stand alone version for Windows and Linux. (Sorry, I don't have a Mac. If someone likes to volunteer I would be glad and put it here.))

You can try to play in the browser with the Burster plugin (http://geta3d.com/).
http://urfoex.blogspot.com/2011/12/ld-22-not-alone.html
(It is currently recommended to use Blender. I don't get the right results in the with Burster ...)

Playing first level:
Right Control -> spawn and jump
Arrows -> move
Goal: Bring the little sphere to the orange curtain.

Playing second level:
V -> spawn and jump
ESDF -> move
Goal: Bring the little sphere to the orange curtain. But first you need to collect the two gems with the big sphere.

Playing third level:
Sorry. Missing.

More stuff later ...

(It's still unfinished. Stuff is missing. And strange things happen.)
[Will make more. Updates will show up @ https://plus.google.com/u/0/116768004614082942458]

Edit:
Interesting:
http://freegamer.blogspot.com/2011/12/ludum-dare-game-jams-and-licenses.html

So I would say that this one has the following license:
--> Code GPL v3 or newer and
--> Assets CC-BY-NC-NA


Edit 2:
I've put up binaries for Windows 23/64 and Linux 32/64. (Sorry, have no Mac)
There is text between and after the levels but it isn't shown. I don't know why.