As former and current board members have identified "a 501-C-6 organization defines an association of persons having a common business interest, whose purpose is to promote the common business interest and not to engage in a regular business of a kind ordinarily carried on for profit." In my brief research I have found that an organization may recieve income from nonmember sources however any income must be considered to be membership support. Also, an organization can have net earnings in the form of an excess of income over expenses. The IRS describes an activity that will jeopardize the 501(c)(6) status as "one that ceases to have as its purpose promoting the common business interest of persons engaged in a line of business" Also, Form 990EZ, Line 4 has a specific line item for Investment Income due to certificates of deposits and other related earnings. Again, the only reference to disqualification of our non-profit status in regards to income that I found is stated above.
Although not a legal opinion it is my general finding that the income from an interest bearing account does not constitute disqualification of the 501-C-6 status as this activity benefits the membership as a whole and is not considered a primary "profit making" activity of the association.
I have a few more resources to check including former board members who have expereince with this topic. I hope to clarify more in the comming week.
A majority of this information was collected from the following publication: http://www.irs.gov/pub/irs-tege/eotopick03.pdf
IRS link to Form 990EZ: http://www.irs.gov/pub/irs-pdf/i990ez.pdf.
