No software exists to do this because it is impossible, let me explain. The mosaic area contains very little information, whereas usually in a 1 inch x 1 inch area, a picture might have 240x240 pixels or 57600 unique total pixels, in a mosaic 1 inch x 1 inch area there might only be 10x10 pixels, or 100 unique pixels. Simply put, the censoring takes 576 different colored pixels, averages them into 1 pixel, and magnifies that pixel to create the mosaic, this is a one way process and cannot be undone.
Here is a simplified version that might be easier to understand. there are 4 pixels in an inch, each one has a number value between 0 and 9, so when you average the four you are left with another number between 0 and 9. an average of 7 for example has many possible 4 number combinations that could produce it, and the more numbers you are averaging, the more combinations are possible.
Well, maybe somebody followed that, in conclusion, let it go, there is plenty of uncensored JAV out there with pretty girls.