This is the problem... In the short run, DDG may be winning small victories. In the long run, they definitely need to build their own index. They need to at least start now, then turn the switch on when it's ready. Of course it's gonna require major infrastructure, but they are building a search engine, so that's a given.

Building their own index is only worthwhile if they can build a good ranking algorithm to go along with it. And they're at a huge disdvantage in doing so because they don't track users to improve quality whereas Bing does.

it could be an open source project, i'd be interested

You could start by playing around with this data: http://commoncrawl.org/

The ways you can interact with it currently are limited, but I think that'll improve.

That project looks amazing. But it'd be nicer to have some sort of compressed raw dump to use different tools.