In short. It is licensed GPL-3.0. The complete source of each version is attached to that version, so the code you can read is the code the binary was built from. There is no public development history, no development issue tracker and no pull requests. You may fork it.

Where the source is

On the release page, beside the disk image. The latest release carries it, and so does every earlier one. The changelog lists them with their notes.

That is what the licence asks for: the source corresponding to the binary distributed, offered to whoever receives that binary. A development history has never been part of it.

Why the working repository stays private

Constants in this application move. The density ceiling became a slider after eight films were measured against it, the chroma stage moved to the other side of the inversion, the two sharpening radii changed unit. Each of those changes how an already-adjusted photograph renders, which is why the first line of every release note says so and why the app never installs an update on its own.

A public repository during that period would scatter builds of a render that is still being calibrated, and the version somebody has installed would stop being a thing I can reason about. You get the source of what you run, and you do not get the road that led to it.

The obvious objection is a read-only mirror: no releases, no issues, no pull requests, so nothing would be scattered and you would get back the blame and the diff. It is a fair objection, and I am not offering one. The reason is not technical: the history holds abandoned experiments and half-calibrated constants I would end up tidying for an audience instead of working. The arrangement suits me (it lets me not justify a constant in public while I am still measuring it) and it costs you any possibility of audit. If that is a deal-breaker, it is a reasonable one, and darktable is free, GPL and entirely in the open.

What this costs you, said plainly

  • No bisect, no blame, no diff between two versions beyond comparing two archives by hand.
  • No public code review. Nobody has read this code but me, and that is worth knowing before you weigh a measurement it reports.
  • No rules travel with the code. No contributing file, no code of conduct, no issue template: what this page says about what the tracker takes lives on this page alone, so a fork inherits the code without them.
  • No pull requests, no roadmap, no design discussion in the open.
  • A fork starts from a snapshot, not from a lineage. It is allowed, it needs no permission, and it is the reason the licence was chosen.

If the project stops

Every released archive stays where it is, and anyone may take the most recent one and continue under the same licence, a right you already have the day you download the application, and one the private repository does not take away.

One exception, stated here instead of found on the first build: the archive holds everything except the keycap button component, a piece of interface and not a piece of the image pipeline. A fork has to replace it with a plain button before the archive compiles, which is about an hour of work and is spelled out below.

The other half of continuity is the infrastructure, which the licence says nothing about. The signing key for updates never leaves my machine, so a fork generates its own and its users install it themselves; the domain and the release repository are mine, and if they go, the archives go with them. Anyone who wants an independent copy of a version should keep the archive, not the link.

Building it yourself, and where that is still incomplete

The archive is a Swift package with its Metal kernels beside it, built on macOS with Xcode and its command line tools. The package manifest states the Swift tools version it expects and the minimum macOS it targets, so those numbers are read there and not off a web page that can go stale.

The exception named above is the keycap button component: a repository of its own, and also what draws the orange key on this site. A build from the archive needs it, so rebuilding the application exactly as distributed is not something a stranger can do today, and nothing on this site lets you tie the disk image you downloaded to the archive you can read. That is a real gap between the licence and what you can do with it.

A binary you build yourself carries no signature, so macOS will ask you about it the same way it asks about the released disk image. The download page explains that dialog.

Third-party code, and what is not derived from it

The image pipeline is Apple's own frameworks: Core Image for decoding and rendering, Metal for the kernels this project writes itself. The updater is Sparkle, under its own permissive licence. The two typefaces used on this site are under the SIL Open Font License. Nothing is taken from another negative converter.

darktable's negadoctor is named on this site as the best public reference on the physics of C-41 inversion, and that is what it is: a reference that was read. No code is derived from it. The physics of the process is public, and that is where the behaviour of this application comes from.

Questions about the licence and forking

Is the development repository public?
No, and it will not become public. The complete source of each released version is attached to that release. There is no public commit history, no development issues and no pull requests.
Is it really open source, and what does “Initiative” mean?
The licence is GPL-3.0 and the complete corresponding source ships with every release, which is what the OSI definition and the four freedoms ask for, so “open source” is exact. “Initiative” is not: it names an intention and a way of publishing, not a group you can join, because there are no pull requests and no public roadmap.
If I fork it, can I keep the name and the icon?
The licence covers the code. The name and the application icon are not code and do not travel with it, so a fork has to be renamed and given its own mark. Everything else the licence grants you needs no permission at all.
What does the licence give me?
You can run it for anything, read the source, change it, and publish your changed version under the same licence. Those rights come with the binary you download, not with a repository you have to be granted access to.
Can I contribute code?
Not as a pull request, because there is nowhere to open one. Bug reports and the files that reproduce them are the contribution that helps most, and a fork under the same licence is explicitly allowed.

Reporting something

The issue list is public and readable without an account; opening one needs a free GitHub account. It takes bugs, decoding problems and the RAW files that reproduce them. It does not take feature votes or design debate: it is one person, and a tracker that promises a conversation nobody has time to hold is worse than one that says what it is for.

The licence arrives with the file

Every right named on this page comes with the binary, not with access to a repository: you download it, and from that minute you may run it for anything, read the source of that version, change it and publish your changed version under the same licence. macOS 13 or later. Apple Silicon and Intel. If this would be your first conversion, the six-step guide is the shorter road.

GET IT

Free, GPL-3.0, and the source of that version sits beside the disk image.