The lifespan of software is a curious thing. Unless a program is deemed irreplaceable by an industry (like Photoshop), most die out or are succeeded by a better -- or cheaper -- option a few years later. Even games, outside of retro collectors' items or unicorn hits (Diablo II), lose steam. After the downfall of Napster, Kazaa, Limewire and the rest of the early file-sharing clients, most people assumed that single source peer-to-peer (P2P) piracy programs -- the kind where you download music or other files from exactly one user -- died out. But one of them, Soulseek, weathered three of file-sharing's mass extinctions, and has quietly remained one of the best sources of obscure music.