Is UMass Amherst a 501(c)(3) entity?

No.

While UMass Amherst resembles a 501(c), the University is tax-exempt under section 115 of the Internal Revenue Code and/or under the doctrine of intergovernmental tax immunity. Section 115 provides tax-exemption for “income derived from the exercise of any essential governmental function.” In Revenue Ruling 75-436, the Internal Revenue Service recognized that citizen education was an essential governmental function.