> Why does one language require portability and not another?
Because more than one language implementation was measured for that language but only one language implementation was measured for the other languages.
If only one language implementation was shown for Ruby it would be Ruby 1.9 - not JRuby
If only one language implementation was shown for Lua it would be Lua 5.1.4 - not LuaJIT
If only one language implementation was shown for Python it would be Python 3 - not PyPy
PyPy and LuaJIT are being treated more favourably than other language implementations.
Because more than one language implementation was measured for that language but only one language implementation was measured for the other languages.
If only one language implementation was shown for Ruby it would be Ruby 1.9 - not JRuby
If only one language implementation was shown for Lua it would be Lua 5.1.4 - not LuaJIT
If only one language implementation was shown for Python it would be Python 3 - not PyPy
PyPy and LuaJIT are being treated more favourably than other language implementations.