However, I found the headline a little bit misleading--I thought "written instructions" meant natural language. On the website, the blurb actually continues "...written instructions called a grammar" which makes it clear this doesn't expect natural language.
In fact, it looks like a 'grammar' is quite similar to most programmings languages, http://www.contextfreeart.org/mediawiki/index.php/CFDG_HOWTO. It makes the iteration and stopping-bounds easy to create. It also allows uses functions to define shapes, so you can use them again easily.
Yes, the distinction between "program that generates images from written instructions called a grammar." and "image file format" is an interesting one too.
Nice idea, but not very revolutionary. I mean, we already have Processing, which is the same but with time included, and which has significantly more interesting efforts in its gallery, if you ask me. I'm not sure what these people are trying to achieve - if it's to get more people into procedural graphics, an (even) more accessible set of tools would be warranted. If it's to create splendid graphics, better tools would probably be warranted (though admittedly I've only checked 10 pictures or so).
On the programming-a-picture front: I always thought that this one [1] is particularly impressive (4 kilobyte Windows executable; zip includes a jpg for if you don't run Windows)
Another open source program in the same space: Structure Synth. http://structuresynth.sourceforge.net/ (Combined with Sunflow to render can make some great images.)
However, I found the headline a little bit misleading--I thought "written instructions" meant natural language. On the website, the blurb actually continues "...written instructions called a grammar" which makes it clear this doesn't expect natural language.