HS1/HS2 and/or Koikatsu are the closest, but they don't really compete with Daz. The only thing they really even have over Daz is lesser hardware requirements, but even that comes with the tradeoff of lower-end/less realistic graphics/renders/etc. There's Blender, which does far more than Daz does, but also a bit harder to use and learn.
There's also Character Creator/iClone and Metahuman, but I believe they're more character-focused/based than Daz is. There's also VAM, but I don't think anyone is actually making with it.