Ah, well, that makes sense. It's implemented on top of Pharo which is a Smalltalk, one of the primary roots of the whole "object browser" idea, eh?

http://files.pharo.org/media/pharoCheatSheet.pdf (Note the "The 5 Panes Pharo Code Browser" object browser.)

See also VPRI's STEPS project: http://www.vpri.org/pdf/tr2012001_steps.pdf