How safe is Nicolas Dorier's BCCSpliter? I noticed a link to this resource on an article talking about safely splitting your BTC and BCH(/BCC):

https://github.com/NicolasDorier/BCCSpliter

Has anyone reviewed the source code and is it safe to use?  Could someone provide a run-down on how it works?  I read the readme but am hoping for a bit more detail.
The readme file pretty much explains everything step by step.

But if you don't have much technical knowledge, the best one to use will be a wallet with some GUI. I suggest you to use Electron Cash.

But before using your private key of the BTC addresses, move those BTC to any other addresses, and then only use the private keys in this software (just a precaution).

You can also import multiple private keys together in this software.

P.S. I cannot comment due to the reputation limit right now, hope this helps you somehow.

Edit: Use precaution while using Electron Cash, as it is as of writing this answer is not much tested and have bugs.