Glyn Moody writes "Two years after its launch, Google's Linux-based Android platform is finally making its presence felt in the world of smartphones. Around 20,000 apps have been written for it. Although well behind the iPhone's tally, that's significantly more than just a few months ago. But there's a problem: few of these Android apps are free software. Instead, we seem to be witnessing the birth of a new hybrid stack — open source underneath, and proprietary on top. If, as many believe, mobile phones will become the main computing platform for most of the world, that could be a big problem for the health of the free software ecosystem. So what, if anything, should the community be doing about it?"