How amazing is this. Now if someone could only figure out how to print a powder without gravity… I just have to hurry up my PhD research I guess. 
http://www.engadget.com/2016/01/07/planetary-resources-meteorite-print-3D-systems/#
Powder print without gravity is already possible. I suspect you are thinking of powder bed prints, which are challenging, true. But for just powder, check out some of the welding style 3d printers, where metal powder is blown into a laser induced melt pool. Nothing about that needs gravity, I think, though some means of collecting the excess powder would be needed.
Good point and it would be interesting to see if those types of Directed Energy Deposition (DED) machines would work without gravity as no one has done it yet. I wonder if the propelling powder, without gravity, would still stick and stay in the melt pool and not be blown off with the remaining excess powder as you state.
Those DED methods are not yet capable of making parts as fine as this because of that blown powder, as well they can’t make parts that require support structures because they can’t do supports.
Now, if we aren’t talking powder based, NASA has shown with Made In Space the validity of extrusion, and they have also developed a wire feed DED system using an electron beam that can be used in space without gravity. http://www.nasa.gov/topics/technology/features/ebf3.html
http://www.engineering.com/AdvancedManufacturing/ArticleID/8778/3D-Printing-and-5-Axis-Machining-Combined-in-One-Machine.aspx - laser based, awesome videos
http://3dprintingindustry.com/2015/02/24/hermle-introduces-mpa-multi-metal-technology-5-axes-cnc-mill/ - non-laser based
Very cool, those remind me of this. It can be used in space and doesn’t need lasers or a heat source. cold spraying
While it would be large and somewhat complicated, one could use a rotating bed that simulates gravity by using centripetal/centrifugal force to hold the powder in a somewhat uniform thickness. Then vacuum off the excess powder and you are done.
centrifuge