Git was first released by linus-torvalds in April 2005. The date given (2005-04-07) is approximate — the first public announcement and initial release occurred in early April 2005, with the first commit in the Git repository itself dated April 7, 2005. Git was developed in a remarkably short time: Torvalds wrote the initial version in approximately two weeks.
Background: The BitKeeper Dispute
The Linux kernel had used BitKeeper, a proprietary distributed version control system, from 2002. BitKeeper's developer (Larry McVoy) provided free-of-charge licenses to Linux kernel developers, enabling the distributed development model the kernel needed. In April 2005, the free license was revoked after a dispute over Andrew Tridgell's reverse-engineering of the BitKeeper protocol (Tridgell was attempting to create a free alternative that could interoperate with BitKeeper repositories).
Torvalds faced an immediate problem: the kernel project needed version control, the existing free tools (CVS, Subversion) did not support the distributed model he required, and returning to BitKeeper was politically untenable. His solution was to write a new tool.
Design Principles
Torvalds designed Git around several principles derived from his experience with BitKeeper and dissatisfaction with CVS:
Impact on FOSS Collaboration
Git's distributed model was directly enabling for the pull-request-based contribution workflow that github-launch-2008 institutionalized. The key insight: if everyone has a full repository clone, anyone can make changes in their clone and propose them back to an upstream repository — without needing write access to the upstream. The patch-based workflow (email patches, apply with `git am`) predated GitHub, but GitHub's pull request interface made this workflow accessible to people who had never used a mailing list.
The transition from centralized version control (CVS, Subversion) to Git effectively changed who could contribute to open source projects. Contributing to a Subversion project required commit access from the project maintainers; contributing to a Git project required only the ability to clone the repository and propose changes via pull request or patch. This lowered barriers dramatically, though it also created the asymmetry between the large pool of contributors and the small pool of maintainers that nadia-eghbal's working-in-public-eghbal-2020 analyzed.
Adoption Trajectory
Git adoption was rapid but not immediate. Through 2007-2008, Subversion remained dominant in many open source projects. github-launch-2008 accelerated adoption by providing a compelling user interface and social layer on top of Git. By the mid-2010s, Git had become overwhelmingly dominant, displacing essentially all other version control systems in open source development and most of commercial development as well.
Git is licensed under gpl-v2, consistent with the Linux kernel. This has occasionally created friction with projects that use permissive licenses and prefer their tooling to match.
Relationship to the mainstream-adoption-and-corporate-embrace-2005-2014 Era
Git's release is the opening event of the mainstream adoption era. The tool that enabled GitHub, which enabled the democratization of contribution, which enabled the corporate embrace of open source development — it traces back to a licensing dispute over a proprietary tool used by the Linux kernel project. The irony is characteristic of FOSS history: the movement's most transformative collaboration tool was created in response to a reminder that proprietary tools remain proprietary.