Possible resolution:

Change in 6.1 [basic.pre] paragraph 7 as follows:

A variable is introduced by the an object declaration (9.1 [dcl.pre]) D of

• a reference other than a non-static data member or
• an object,

where D that

• is not the parameter-declaration of a template-parameter and
• does not declare a non-static member (11.4.1 [class.mem.general]).

(From submission #1005.)

The definition of "variable" in 6.1 [basic.pre] paragraph 7 does not clearly exclude non-static data members, because those are also declared using an object declaration as defined in 9.1 [dcl.pre] paragraph 8.