I also can confirm this worked on Windows.
Spoon.bat
==
REM **************************************************
REM ** Setup Karaf endorsed libraries directory **
REM **************************************************
#set JAVA_ENDORSED_D...
#if not "%_PENTAHO_JAVA_HOME%"...
#set JAVA_ENDORSED_DIRS=%JAVA_ENDORSE...
==
Had to edit with 'wordpad' as the end of lines were funkey; 'notepad' did not work at all. Just added '#' to the beginning the three lines as above.
Troy.
#