I have some products that I'd like to purchase but some of them state that to render I have to use Firefly Render Engine in Poser 5.  I don't have P5 only D/S so is there a work around this or is this just an old hanger on that has been modified in the new versions of D/S?

It depends. Poser 5's Material Room has a lot of functions that D|S currently lacks, and asking for Firefly certainly suggests that at least some material room settings are being used. However, D|S (when rendering with 3Delight) does support some features of the Poser 5 material Room (displacment, reflection, refraction, maps to control the strength of features such as specularity) so it might be possible to hook things up to work (but you'd have to do it by hand, or find someone who'd already done it and was willing to share their presets).