Lucis Pro was available on the LucisArt website, but it seems that the domain doesn't exist anymore, therefore making it impossible to acquire the software. I've seend some discussions about it on the DPReview website (a website specialized in photography and software related to this category), but nothing conclusive as to where to download or buy it.
Try using Adobe Lightroom as an alternative to Lucis Pro, or look on the installation CD for your camera, in case you have one.