Marie, many people confuse what it means to be non-profit/not for profit and/or an exempt organization for HOA purposes. To further confuse the issue, you can have one designation for state purposes and another for federal. Does your HOA file a Form 1120, Form 1120-H or Form 990 for Federal tax purposes? This will have a bearing on how interest earned may be taxed.
Generally speaking,
an HOA that files a Form 990 qualifies as a non-profit organization for Federal tax purposes(very few HOAs actually qualify),
an HOA that files a Form 1120-H is an exempt organization for Federal tax purposes (must meet certain guidelines, but "exempt function" income is not taxable),
an HOA that files a Form 1120 is neither a non-profit nor exempt organization for Federal tax purposes.
In any case, earning interest generally does NOT disqualify an entity from being a non-profit organization, if that is indeed how your HOA is established.
I have found that Porter & Company CPAs website is an excellent resource for general questions regarding HOA accounting and tax issues (http://www.porterandcompany.com). They have some excellent articles that are relavent and timely. I am a CPA and a former Board member of my community's HOA, however, I do not specialize in HOA taxes and thus leave those issues to the experts.
You will see a number of different opinions on any accounting or tax issue on the message boards. You will notice that I use the word "generally" liberally in my response. It is the CPA dictionary they give us in college.

As EVERY case involves a different set of facts and circumstances, my recommendation is always to rely on your audit and/or tax services firm for the final say on such issues.
That being said, the HOA for my community does have its reserve funds in an interest bearing account. While it does not earn a stellar interest rate (what financial institution does these days?), anything is better than zero, right?!?