Must all nonprofits be purely about helping others?

Summary:

No. That requirement applies to foundations and public charities (501(c)(3)s), but there are many types with other requirements

Someone wrote in Nonprofit (http://www.rain.org/mailman/listinfo/nonprofit) in September 2002:
"The idea for a non-profit is not self gain, but to help others."

Robert D. Shriner, Ph.D. (rshriner@aol.com) replied on September 28::

That may be the objective/requirement of a 501(c)3 organization in the US; but
it is not a requirement for other US non-profit organizations, including coops,
trade & professional associations, community development organizations, etc. (See http://www.nonprofits.org/npofaq/16/08.html.)

These are all authorized under US law to be tax exempt because of their "public interest" and "mutual benefit" character; but donations to such organizations generally
do not qualify for deductibility from federal income tax.

University-based
academics and artists regularly submit proposals and receive funding for their
research and artistic projects through their educational institutions.
However, the institutions are obliged to provide regulatory oversight and
detailed reporting on the use of those funds.

As has been previously noted,
only nonprofits whose mission includes the specific activities of the funding
agencies are able/willing to serve in that "sponsoring" capacity. (See also http://www.nonprofits.org/npofaq/18/50.html.)

The above is a somewhat oversimplified summary of the situation; but it is
generally sufficient for most purposes. Before trying to raise funds, start a
nonprofit organization, or make commitments to donors, it is essential to get
legal advice from an attorney with extensive experience in the formation and
operation of US nonprofit organizations. This is NOT something that most
attorneys have experience in doing!