I recall someone suggesting a statement be added to the application form that applicants are not members of another party, because otherwise the Pirate Party could be considered a 'component party' (I think this is right) [EDIT: I think it might have been someone from the ALCP posting on the discussion board, but I can't remember where]. I guess the relevant part of the Electoral Act would be
section 3(1) (linked)? The Greens require applicants to agree to
such a statement (linked), so I guess they see this as a potential issue. If the membership fee is being changed, then the application form will need to be edited, so it might be an opportune time to consider this change too.
Looking at the
Electoral Commission's requirements (linked), it seems that the final declaration statement on the membership form "I declare the information provided on this form to be true and complete." isn't strictly necessary, so perhaps this could simply be replaced with "I am not a member of any other political party." (or similar.)