~Safety: This should be as safe as using the official LiteOn flasher. Because it is the official LiteOn flasher... with a few minor tweaks made to the firmware packaged within.
~Safety II: LiteOn drives also have the advantage of always being recoverable because they use the MediaTek chipset. You can flash a LiteOn drive with a completely wrong firmware and still be able to recover it (it might be a bit complicated, but it can be done). Only way to truly kill a LiteOn is to deal physical damage to it.
~Safety III: So I think it's perfectly safe. Nobody has reported any problems. But that being said, please do be aware that LiteOn does frown upon the use of unofficial firmwares. Their tech support will not help you if you use this patched flasher. Recognize that you are taking a risk (a small one, but one nevertheless) and be prepared to accept any negative consequences that may result from this.
~Side effects: The changes made to the firmware are fairly minor--all that has really been changed is that two entries in a data table got swapped. The writing functions, reading functions, etc.--all the important areas of the firmware--were untouched. The only side effect is that buring media with the RICOHJPNR02 media code (8x-certified Ricoh +R media) will result in lower-quality results than before. This is because better write quality was achieved for the RICOHJPNR01 media code (4x-certified Ricoh +R media, such as the Fuji and Maxell) by swapping its writing strategy with the RICOHJPNR02 code. So this firmware has a trade-off: it improves the R01 quality at the cost of R02 quality (in the future, I will make a patched firmware that doesn't have this side-effect, but that will take some time, so in the meantime, this is all that I can offer). If you don't burn any R02 media (and most people don't, because if they can get the same quality burning R01 media at 8x, why pay more for the R02?), this shouldn't be of any other concern. There are no other side effects aside from this. Burn quality for all other media types will be unaffected.
~Official from LiteOn... LiteOn will most likely never release any firmware for the 812S that will enable 8x burning for the Ricoh R01 media. The only way to do it is to use a patched firmware.