Stein realized when designing Sage that there were many open-source mathematics software packages already written in different languages, namely C, C++, Common Lisp, Fortran and Python.

However, Sage contains hundreds of thousands of unique lines of code adding new functions and creating the interfaces among its components.

[8] The same year, Stein described his disappointment with a lack of academic funding and credentials for software development, citing it as the reason for his decision to leave his tenured academic position to work full-time on the project in a newly founded company, SageMath, Inc.[8] Both binaries and source code are available for SageMath from the download page.

If SageMath is built from source code, many of the included libraries such as OpenBLAS, FLINT, GAP (computer algebra system), and NTL will be tuned and optimized for that computer, taking into account the number of processors, the size of their caches, whether there is hardware support for SSE instructions, etc.

SageMath 8.0 (July 2017), with development funded by the OpenDreamKit project,[8] successfully built on Cygwin, and a binary installer for 64-bit versions of Windows was available.