No it doesn't have to be. The ram in the qualified vendor list has been tested & confirmed to be compatible with mobo, so it's a good recommendation but doesn't mean that no other ram will work either.
Do make sure that the ram you get is an identical pair & the specs for that pair match the original pair in the mobo.
No most ram will be accepted.. you need to make sure what your FSB is to make sure that it will actually run at those speeds. Also you need to make sure if they are Buffered or ECC some dont accept them if they are they might need to be unbuffered and non-ecc..just make sure of that..