After nearly two years of development, Mozilla officially launched Firefox OS devices in stores, and has opened up payments for developers interested in charging for their apps – or charging for content inside their apps. The first commercial Firefox OS devices arrived in Spain, ready to be sold by Telefónica on July 9th; Poland, Colombia, and Venezuela also will have launches in the near future. Mozilla is starting by undercutting the low-end market to build momentum, but that’s not to say that higher-end devices aren’t in the pipeline for the future.