From complex interactions between individual character and cultural influences, ethical challenges can arise at all levels in all types of organizations. (So, for-profits have no monopoly on greed.) Some ethical challenges can lead to criminal violations, e.g., fraud, misappropriation of assets, misrepresentation; but, the more common ethical challenges are on the fringe and can relate to, say, conflicts of interest, misallocation of resources, or inadequate accountability and transparency. Therefore, it is not easy to see what unique "rules", compared to what applies here and there, sometimes quite differently, in the private sectors of different countries, might "measure" the ethics of nonprofits. However, it may be that nonprofits are more likely to face certain types of ethical issues, related for example to compensation, investment policies, solicitation and reporting (meaning, transparency), etc. Notwithstanding, in all types of organizations, one can say that the same four crucial factors of moral awareness, moral intent, moral decision making, and moral action should guide ethical conduct. Moral Courage in Organizations, available at https://www.researchgate.net/publication/254583225_Moral_Courage_in_Organizations, may be of interest.

Article Moral Courage in Organizations

Maybe you have a look at this paper:

Starke, C. (2012): "Serving the Many or Serving the Most Needy?", Economics of Governance, 13(4), 365-386, (DOI: 10.1007/s10101-012-0116-8).

You could examine the literature related to “self-dealing” practices -such as Herzlinger (1995)- and all the ways non-distribution constraint can be eluded. The deviation from market prices can be a proxy.