I don't know if you actually see any of our replies, but I'll try to help you again. I don't know much about Daz or how it handles rigs and animation, but if you can export a BVH, you can use that BVH information on a dummy rig in HumanIK and then retarget the animation to your current rig in the same scene. Just import the BVH to a temporary HumanIK rig in the scene, then use the Source on your current rig to point to that other BVH animation. You will need to retarget the BVH rig to match your HumanIK rig for best results, but that's basically how to transfer the animation.
I'm sure you know that if you are using animations in Daz that you purchased from a different content vendor, then you are probably prohibited by their EULA from reselling those animations in any other format. I'm not suggesting that is what is your intent here, but it's probably fair to assume anyone posting here is working on commercial projects for distribution in some way so just thought I'd remind you to check the EULA for anything you use from Daz. Anyway, good luck with your project.