The world of digital music is now dominated by lots of useful proprietary tools--with Apple's ruling the roost--but there are also many free open source tools and applications worth looking into. Of these, Rockbox, an open source firmware replacement for MP3 players from manufacturers ranging from Archos to iRiver to Apple, is easily one of the most popular. Lisa originally covered Rockbox in this post, and we covered it again here. Now, in an interview, several of Rockbox's developers are weighing in on its benefits, its user base and its future. Rockbox has been around for over a decade, and especially if you have an older MP3 player that you would like to add functionality to, it can greatly improve your digital music experience. It's essentially like having..