SageMath (often, just Sage) was started in 2005 by William A. Stein as a free open-source alternative to to Magma, Maple, Mathematica and Matlab. Unlike the latter systems, as well as many other free and commercial computer algebra and other math systems, no special purpose language was invented for the system --- instead, it uses Python.

Nowadays SageMath has hundreds of developers around the globe, is widely used in research (university and commercial - it is a weapon of choice for many cryptographers) and teaching at university and high school level.

SageMath has been supported by various science and engineering funding bodies in US (NSF) and Europe (EU Horizon 2020 programme) via grants,
but all such support is fixed term, whereas the project constantly needs funds for running infrastructure, and for engineering work which is too far from the principal, related to mathematics, part of the project, or just too specialized. We plan to use sponsorship income to cover infrastructure costs, and to hire software engineers for specific tasks.