Babel Development Log

The translation system is first and foremost an Open Source project, so it needs to be released under at least one OSD-compatible licence. Broadly speaking there are three classes of licence from which to choose:

• fully reciprocal licences (such as the GPL),
• reciprocal licences with a library exception (such as the LGPL), and
• non-reciprocal licences (such as the modified BSD licence).

My preference is for a fully-reciprocal licence because that encourages other developers to give back to the community by releasing their own programs as Open Source, and the most widely used licence which does this is the GPL. However, I also want the translation system to be used as widely as possible, and imposition of the GPL by itself would prevent such use:

• by Open Source projects that have chosen a licence that is incompatible with the GPL, and
• by proprietary vendors who either cannot or choose not to release under the terms of an Open Source licence.

For this reason I want to retain the ability to grant further licences, including fully commercial ones if the recipient is not giving back in some other way. Currently that is straightforward because the code is entirely written by me, but the situation becomes more complicated if third-party contributions are added to the codebase.

In the case of the library itself I don’t foresee any substantial third-party contributions being needed, but for the language definition files they will be essential if the project is to be a success. There are several ways to preserve my ability to issue new types of licence:

• by assigning copyright to me;
• by giving me the right to sublicense on terms of my choosing; or
• by licensing contributions permissively enough to coexist with any other licence I might want or need use.

Sun use a combination of the first two methods for contributions to Java and MySQL, and there are other companies with similar arrangements, but they are sometimes criticised for being overly one-sided. I wouldn’t personally object to contributing on such terms, but can see why others might.

I won’t claim that the third method is completely fair — dual-licensing schemes generally aren’t — but it is at least fairer than the other two. The protection it provides is weaker, because not all of the code is covered by the GPL, but still much better than placing everything under the BSD licence or the LGPL. I think it is an effective and defensible solution for the current situation where the project is first and foremost my work. (If others start making contributions of comparable size and value then I’m willing to negotiate.)

I’ve not settled on a precise form of words yet, but it will most likely be similar to the copyright disclaimer used by the GNU Project.