Selling products and services would make them a hybrid (for-profit/non-profit) organization. The sales would be subject to sales tax. Without a 501(c)(3) status, they also wouldn't be eligible for many grants to secure larger fundings.
Just look at the American Red Cross, they sell the blood that is donated to them.
You of course can't have a profit that is distributed at the end of the year. But you can keep "profits" in the organization for furthering the goals of the 501c3.