Not surprisingly, the executive and board positions of the WMF follow U.S.
convention. It's not super typical to mix the "executive director"
nomenclature with president / vice president, but its common to have vice
presidents reporting to a chief executive (who will often take the title of
"President & CEO.").
As for conflicting names with Board titles... In the U.S., its far more
common for boards to have a Chairman (or Chairwoman) and a Vice-Chair, than
president or vice-president (which connote operating roles).
Personally, it would be easier for me to understand the org chart of the
WMF if they picked a particular nomenclature and stuck with it. For years
they've been mixing systems - CTO and executive director, vice president
and a proliferation of "Heads of" this and that (a highly uncommon
executive title in the U.S., as far as I can tell), directors of some
things and chiefs of other things... It's a bit strange.
On a side-note, it's interesting to see that Erik has been moved out of the
"executive" section of the staff list and into engineering.