Apache License 2.0

The Apache License 2.0 is a permissive open-source license maintained by the Apache Software Foundation. Like other permissive licenses it allows broad reuse, modification, and redistribution in source or object form — including inside proprietary products — while disclaiming warranty and liability. What distinguishes it from minimalist licenses is engineering for the real world: an explicit patent grant, a structured attribution mechanism, and language precise enough that corporate counsel can approve it without a meeting.

The patent grant

Each contributor grants every user a perpetual, worldwide, royalty-free, irrevocable patent license covering their contributions as combined with the work. Crucially, that grant terminates automatically for anyone who initiates patent litigation alleging the work infringes a patent — a built-in retaliation clause that makes suing over Apache-licensed code self-defeating. This gives downstream users protection that the shorter MIT License does not spell out, which is why Apache 2.0 is the default for larger, multi-contributor projects where patent exposure is a genuine concern. In effect, the license converts a project's contributor base into a mutual non-aggression pact.

Attribution and the NOTICE file

Redistribution requires keeping the license text, copyright notices, and a statement of significant changes. If the work ships with a NOTICE text file, redistributors of derivative works must reproduce its attribution notices, though they may append their own. The NOTICE contents are informational only and do not modify the license terms — it is a credits reel, not a contract amendment. When recording the license in metadata or package manifests, its SPDX identifier is Apache-2.0.

Where you meet it in this ecosystem

Apache 2.0 is everywhere in the sovereign stack. Large swaths of open AI infrastructure and many open-weight model releases use it, which matters when you check a model card before depending on the weights: Apache 2.0 means genuinely unrestricted use, unlike the custom "community licenses" that carry field-of-use restrictions. In the Bitcoin world it is a common choice for infrastructure — the Eclair Lightning implementation, for example, ships under Apache 2.0 — and across mining tooling you will find it wherever authors want maximum adoption with patent safety. Because it is not copyleft, derivative works may be closed or re-licensed so long as the license text, any NOTICE, and a statement of changes travel with the distribution; whether that is a feature or a bug depends on your theory of how software freedom is best preserved.

Compatibility and choosing a license

Apache 2.0 vs MIT in one minute

Both are permissive; the difference is explicitness. MIT fits on a page: keep the copyright notice, no warranty, done — its silence on patents is tolerable for small utilities but uncomfortable for anything patent-adjacent. Apache 2.0 spells out the patent grant and its retaliation clause, defines "contribution" precisely, handles trademarks explicitly (it grants no trademark rights), and standardizes attribution through the NOTICE mechanism. The practical rule of thumb: MIT for small libraries where friction matters most, Apache 2.0 for substantial projects with many contributors or any plausible patent surface. Downstream, both let you do essentially anything except sue the people who gave you the code.

Apache 2.0 is one-way compatible with GPLv3: Apache-licensed code may be incorporated into GPLv3 projects (the combined work being GPLv3), though not into GPLv2-only ones, whose lawyers read the patent-termination clause as an added restriction. That one-way street is a practical bridge between the permissive and copyleft worlds. D-Central's own releases sit on the copyleft side — DCENT_OS is GPL-3.0, chosen so that improvements to code running on people's miners must remain open — and the GPLv3 compatibility means Apache-licensed components can flow into such projects, another quiet way the permissive ecosystem underwrites the copyleft one. Both are honest open-source choices; read the obligations, not just the label.