As I threatened a while back, I've started up a "Pharo shim" - a package that adds to a Squeak image those messages necessary to get interesting Pharo projects working in Squeak:
http://www.squeaksource.com/PharoCompatibility
At the moment "interesting projects" means "PetitParser", and so the shim merely contains Symbol >> #isBinary.
Going forwards, as I find other bits necessary - my upcoming Helvetia/LanguageBoxes work will no doubt uncover bits and pieces - I'll add to Pharo-Compatibility.
I expect some bits to make their way into trunk, and we can regard Pharo-Compatibility as a proving ground of sorts.
frank