The current editor uses a native implementation based on .Net for Windows, and Cocoa for Mac OSX.
It crashes every time I run it.
You might want to file an issue at the http://bullet-physics-editor.googlecode.com
issue tracker. It needs a recent .Net 3.5 or later installation I think.
If those crashes and incompatibilities persist, we might migrate to wxWidgets.
A related project, OgreKit/GameKit, uses wxWidgets and OpenGL for a node editor. It builds on Windows and Linux using the cmake build system, we still need to fix Mac OSX cmake support. See http://code.google.com/p/gamekit/downloads/list