I understood from this meta question that MathOverflow is a nonprofit nonstock corporation dedicated to keeping this site running and that the nonprofit status allows receiving donations. What is the financial situation of MathOverflow? If a little more money would help keep the site operational or increase relevant outreach activities, how can I donate?
Update: Donations are now possible, see this post: Donations to MathOverflow, Inc
[Apologies for the long delay in answering, I was on my honeymoon! I may update this quick answer after I get back to regular life.]
Up until now, MathOverflow has been paying for regular expenses through a generous grant from The Alfred P. Sloan Foundation. Coincidentally, that grant recently dried up and we are currently making arrangements for other funding. Part of this consists in applying for new grants to support specific projects. We are also setting things up so that users can donate funds for specific or general purposes. And we are planning a first fundraising campaign.
As many are aware, MathOverflow is a 501(c)(3) nonprofit organization and is therefore capable of accepting tax-deductible donations from individuals, corporations and unions. If you want to make a donation before our first fundraising campaign, contact firstname.lastname@example.org and we will discuss modalities.
I'm an employee of Stack Exchange and can only give a partial answer. The hosting and maintenance cost of the main MathOverflow site, Meta MathOverflow and the chatrooms hosted on http://chat.stackexchange.com/ are covered by Stack Exchange. This is actually less generous than it might seem since the incremental cost of hosting MathOverfow is minimal considering we already host 130+ other sites on the same engine. We consider MathOverflow a marvelous gem of a community and are honored you have joined us. So for the foreseeable future, this site will remain operational as a part of the Stack Exchange network.
When people ask us where they can donate, we tell them:
The best way to help is to provide great answers to other questions as you can, or help out with a multitude of janitorial tasks such as:
- Editing posts to fix grammar, spelling, formatting, broken links and similar
- Creating and editing of Tag wiki pages
- Reviewing first posts by new users, and eventually posts with votes to be put on hold
- Voting to indicate the quality of content when you have sufficient reputation to vote
I can't speak for the MathOverflow corporation, however. We support some outreach by sponsoring people promoting the site at conferences, but MathOverflow might be interested other promotions. In addition, there are almost certainly costs separate from hosting this site. Finally, if MathOverflow ever decided to leave Stack Exchange (which would personally make me sad), hosting costs would need to be be covered somehow. I'll leave it up to a representative of MathOverflow to answer the question of how to donate and what the money would be used for.
I am also not a representative of the MathOverflow Foundation. Most of the people I know who are are also moderators, and I will let them speak officially. Below is my idea of what they would say:
"The current monetary costs of maintaining the foundation itself are currently covered by existing donations from certain grants. The current costs in time of maintaining the foundation as well as moderating the forum with Stack Exchange are at present covered by community volunteers, the (unpaid) moderation team, and assistance from the Stack Exchange community team.
"There are a number of side projects being considered, including a proper reception of donations of money. Most though require planning, consideration, and more volunteer time, such as deciding how to 'archive' MathOverflow, how to promote it, and how to make it thrive.
"The last is most important, making the community thrive. Community moderation, community recruitment, and quality questions, answers and comments provided by the community are the most desired contribution, both on the main forum and on meta. Being a good community member is the major donation we ask."
Gerhard "Self Training As Volunteer Spokesperson" Paseman, 2015.07.31