Making a web application open source [closed]

Question

I have worked for quite a long time on a web app, some kind of CMS and Intranet portal developped in PHP/MySQL with jQuery.
At the moment, the repository is under SVN, but I think I will migrate on GIT before making it public. I am wondering if some of you might know what's the best method, or just give some advices, or share some links regarding the fact of making a web app public, and trying to attract developers on the project.

I don't know which license I will be using (GPL, MIT ?), neither the platform on which I want it to be hosted (Sourceforge, Github, Google code). Any advice about that would be great too.

Thanks for your help.

Answer 1

I have very good experience with Google Code. It is fast, has no technical issues and the online interface is very clean and easy to use (unlike SourceForge).

I recommend either GPL or AGPL license.

AGPL is Affero GPL. It is pretty much the same as GPL, except anyone who publicly uses modified version has to provide its source code. For example if some company made extensive modifications to the code only for its own website/project, it would not be forced to release the changed source code if you used only GPL. But under AGPL, the company would have to release code even though it didn't distribute the application, but used it on its own server only - contributing to the public code base. This could deter some potential users from corporate sector though, so you have to weigh its advantages and disadvantages!

EDIT: Just for inspiration, there is list of projects using AGPL: http://en.wikipedia.org/wiki/List_of_AGPL_web_applications

EDIT 2: Reacting on comment by David Dorward on the question.

There are two possible reasons why you would want to choose open license.

1) Political. You want to go open, because open is the morally right way to go. You should choose AGPL or even MIT License.

2) Practical. You want attention and people using your project. Open source projects gather attention much more easily that similar closed source (or even commercial) projects. If your project is looking promising, you may get people who will actively contribute into code base - for free. Also, distributing free PHP closed source application is somewhat complicated (though not entirely impossible). GPL is the way to go.

EDIT 3: I recommend this free book: Producing Open Source Software