Mojo Goes Fully Open Source Under Apache 2.0, a Week After Hitting 1.0

Mojo Goes Fully Open Source Under Apache 2.0, a Week After Hitting 1.0

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Modular open sourced the entire Mojo compiler on August 18, releasing it under Apache 2.0 with LLVM exceptions. The release includes the compiler, the tools, and everything needed to build the language from scratch.

It comes a week after Mojo 1.0 shipped on August 11 as part of the Modular 26.5 release, marking the language’s transition from a 2023 experiment to something the project is willing to call production-ready with API stability guarantees.

What Mojo is

Mojo was created by Chris Lattner, the architect behind Swift and LLVM, alongside Tim Davis. The pitch is Python’s syntax with systems-level performance and Rust-inspired memory safety, built on the MLIR compiler framework so it can target heterogeneous hardware: CPUs, GPUs, TPUs, and ASICs from the same source.

The motivating problem is the one every machine learning engineer has hit. Python is where the ecosystem lives, and Python is too slow for the parts that matter, so the performance-critical code ends up in C++ or CUDA behind a Python binding. You maintain two languages and a boundary between them. Mojo’s proposal is to make the fast path and the ergonomic path the same language.

The 1.0 milestone

Reaching 1.0 means backward compatibility and API stability, with future 1.x releases expected to be primarily additive. For a language that spent three years changing under its users, that is the more consequential announcement of the two.

Open source, with an asterisk

The source is public under a permissive license, which is a real change from Mojo’s earlier status as a proprietary compiler with an open standard library.

Modular is not yet accepting outside contributions to the compiler or tools. The standard library has taken community contributions since 2024, and the project says it plans to start accepting compiler contributions by the end of 2026.

So this is “you can read it, build it, fork it, and ship it” rather than “you can send patches.” That is a meaningful distinction for anyone evaluating the language on governance grounds, though it is also a normal intermediate step: opening a compiler’s source and opening its development process are different amounts of organizational work.

The Qualcomm context

The open sourcing follows Qualcomm’s acquisition of Modular, which several outlets have connected directly to the licensing change. Qualcomm has an obvious interest in Mojo’s heterogeneous hardware story given its own silicon, and an equally obvious interest in not having that story depend on a proprietary toolchain that customers are reluctant to adopt.

Trying it on Linux

Mojo runs on Linux and macOS. The toolchain installs through Modular’s own tooling, and with the compiler now open source, distribution packaging becomes possible in a way it was not before, though nothing has appeared in the major repositories yet.

Whether Mojo finds an audience beyond machine learning workloads is still an open question. It has been positioned primarily as an AI language, and general-purpose adoption is a much harder sell against Rust and Go for systems work. Open sourcing the compiler removes one of the standard objections, which was never the main one.

More news

Mojo 1.1 Opens Its Compiler to External ContributionsModular now accepts external contributions to the Mojo compiler and has moved internal compiler issues to public GitHub trackers, which is the step that distinguishes open source from published source.Rust 1.98 Adds Algebraic Float Methods, Bringing -ffast-math Style Optimization Without Undefined BehaviorNew algebraic_add, algebraic_mul and related methods on f32 and f64 let the compiler reorder floating-point operations for vectorization. The result is non-deterministic but never undefined, which is the important distinction.Go 1.27 Ships Generic Methods, a New JSON Engine, and Goroutine Leak ProfilingGo 1.27 lands with method-level type parameters, encoding/json/v2 backing the standard JSON package, a generally available goroutine leak profile, faster small allocations, and post-quantum ML-DSA signatures.

Background reading

Explainers for the concepts behind this story.

Debugging Bash Scripts: set -x, PS4, and ShellCheckHow to find out what a misbehaving shell script is actually doing: syntax checks with bash -n, tracing with set -x and a better PS4, tracing to a file, catching errors with trap, and finding bugs before they run with ShellCheck.getopts Explained: Parsing Script Arguments Without RegretReading positional parameters works until someone passes flags in a different order. getopts is built into bash and handles short options properly, getopt handles long ones, and there is a reason to avoid one of them.Shell Completion: How It Works and How to Write Your OwnWhy Tab knows your command options, where completion scripts live, and writing one for your own tool in bash and zsh.