I was able to compile blender via scons on my Mac. From this tutorial (archive).

Than I decided to edit existing icons … and that is my question.

Edit SVG?

If I do changes on SVG file placed in ~/blender-build/blender/release/datafiles, I save SVG and run python blender_icons_update.py I can see for a moment two PNG icon files, but they disappear. Compiled blender from terminal python scons/scons.py -j 5 results with original icons. Did I omit something?

BTW - Wiki page has a note which I don't understand: "... both inkscape and blender must be in the system PATH for this command to execute properly."

I understood PNGs are generated from SVG, but for some part of icon edit it's easier to edit PNG for me. Is it possible to generate icons from PNG too?