Do you have a better idea?

This is an iterative process. Yes, GlobaLeaks could be used to spread fake leaks, but then it will force all democratic processes to be more transparent, in order to efficiently prove or disprove leak L or new N.

How fast we can prove a piece of fact is the next step, but to get there, you have to give people the tools to spread information (true and fake) as much as possible, imho

Edit : Also, this initiative is European. If you don't trust your own intelligence services, stop whining about it and come live in Europe?

An intelligence agency can already leak stuff to the press while remaining largely anonymous, this doesn't improve their situation nearly as much as an actual whistleblower.

who was the whistle-blower in the Hillary emails?

Someone else gave the Pentagon papers as an example of a "good leak" and it was. But I think good leaks tend to be those, like the pentagon papers that are handled by responsible organizations (NY Times and Wash. Post in that case). The people who created this code may be just such people, but there's no reason to think someone who does git-clone on this repo is.

By the way, both the Post and the Times openly solicit leaks.

You're missing the point. If you assume some intelligence agency was behind the Clinton email leak, they could have anonymously leaked them to a range of press outlets and generated the same result. Meanwhile, Ellsberg had to work incredibly hard to prevent being caught before the Pentagon Papers went public. A site like this makes Ellsberg's life easier, while making no difference to the intelligence agency.

The method of leaking has little to do with the value of the leak, someone will print almost anything. The Times and the Post regularly print items intentionally leaked for propaganda purposes, the classic example is the buildup to the Iraq War.