Atmosphère is currently being developed and maintained by SciresM, TuxSH, ktemkin and hexkyz.
In no particular order, we credit the following for their invaluable contributions:

switchbrew for the libnx project and the extensive documentation, research and tool development pertaining to the Nintendo Switch.
devkitPro for the devkitA64 toolchain and libnx support.
ReSwitched Team for additional documentation, research and tool development pertaining to the Nintendo Switch.
naehrwert for the hekate project and it's hwinit code base.
hedgeberg for research and hardware testing.
lioncash for code cleanup and general improvements.
All those who actively contribute to the Atmosphère repository.

Languages

C++ 89.6%

C 7.1%

Makefile 1.7%

Assembly 1.2%

Python 0.4%