This depends on whether the photographer means "not for profit" in its colloquial or its technical sense.
We may all think of Wikitree as a not-for-profit because it doesn't charge for access to genealogical information. However, it does generate revenue by selling advertising (which is seen by non-members on the Wikitree site). Moreover, "Wikitree" is a brand of interesting.com Inc., which is registered in New York as a business corporation. The operator of Wikipedia (that is, the Wikimedia Foundation) has taken the effort to register as a non-profit organization with the IRS and state regulators, but interesting.com Inc. has not, and thus there are no publicly available records of interesting.com Inc.'s revenues or profits (that is, no IRS Form 990, which non-profits are required to file with the IRS and which are available on such sites as guidestar.org). This is also why Wikitree uses a .com rather than a .org web address (unlike familysearch.org and geneanet.org). Basically all we (at least outside the leadership team) have to go on is Chris Whitten's assurance that he is running this as a not-for-profit; there is no actual transparency or accountability for this.