(I'm an amateur in this regard, so these are just my somewhat educated guesses)
When I did try it at some point almost 5 years ago, I used
JavPlayer. As far as I understand, any such software is just basic* decensoring software (i.e. you can't really remove it, you can only restore what was there with some degree of certainty, but never 100% since some information is bound to have been lost — after all, censoring is basically reducing the density of information carried by an area of an image, i.e. a group of pixels)
With the current technological paradigm, let's call it that, I think we (almost) always have (a certain) AI/machine learning framework/neural network doing the work, and when I tried to dig further into what's happening under the hood, I found that abbreviation
GAN is used quite often, which stands for "generative adversarial network". If you search even for a bit for any decensoring solutions, it seems that you're bound to encounter it. But it's just one of the approaches
I feel that with the advancements of neural networks etc. in the last few years, decensoring might have become better and/or faster, but from what I see on JAV sites, it's either not very noticeable in practice, or still demanding and therefore not really cost-effective for "free" sites living off ads, or we just have a mixture of older and newer decensoring attempts (possibly a mixture of all three is what's really happening)
Still, in some cases, even such attempts are better than nothing, and I've had
a great case for it not so long ago
* Meaning also that I doubt there is anything specific about the "JAV mosaic", so I would assume that you could use any kind of video decensoring software to decensor JAV