The difference is that the SlabFree Chapter does not endorse "The List" as a matter of Chapter policy. "The List" is not a part of the Slab Free Chapter. However as Chapter President Peter Sanders has indicated, there are club members who belong to the SlabFree Chapter and who have also signed "The List".

It's like belonging to the Atlantic Chapter Member does not automatically make one a Las Vegas Chapter Member.... and policies that the Atlantic City Chapter may or may not endorse does not apply to policies that the Las Vegas Chapter may have in effect... but there may be individuals (like Andy Hughes as an example) who belong to both Chapters.

I can't explain the differences any clearer than that Mark.