Making tax-deductible donations to fund SageMath development
If you would like to make a tax-deductible donation to support the development of SageMath see the University of Washington's Sage Foundation Donation Page. Contact UW Professor William Stein at firstname.lastname@example.org for more information.
The Sage Foundation budget pays for things like the SageMath booth at the Joint Mathematics Meetings, some travel towards Sage Days workshops (especially when grants can't cover the travel, due to US-citizen-only restrictions for some grants), significant student work on SageMath (usually paid at $20/hour), etc...
The donations during the last year were a lot more than in all previous years combined, including $5K from Microsoft Research, $5K from the founder of an internet company, $50K from the Beatrice Yormark Fund for Women in Mathematics, $25K from a Wall Street mathematician, and a few other smaller donations. Donated money doesn't expire, and the university does not charge any overhead fees to administer it. In contrast, the university does charge large overhead fees on federal grants.
The Sage Foundation account is a University of Washington Mathematics Department account. William Stein plans to be on unpaid leave for the next two years while he runs this company, during which time he's still fully affiliated with the university, but of course he can focus 100% on building a company. However, after two years he may be forced to resign. However, there are three other faculty members in his department who are SageMath developers and ardent supporters of what he's doing, so he thinks things would be fine in two years. Also, he has a very good relationship with the math department itself. He's very much not quitting in disgust, but focusing 100% on his goals with CoCalc and a business. (He has been trying for a long time to do both and it is too difficult for him to balance competing interests.)