As of 2018.08.12, this script is working WITHOUT ROOT / BEING BLOCKED, although I DO NOT take responsibility for your banned account!
(Alghough I highly doubt it, this script runs at human speed,
and we don't & won't do anything causing them - coder - trouble.)
(I myself, of course, use the script on my main and only account daily,
if this fact can make you feel better.
Nothing is 100% safe, even Blizzard, Valve and Riot Gaming sometimes banned the wrong accout - but
I'd say it's like 90% safe.
They have other higher priority things to do.
Considered the fact that more and more Japanese mobile games started to support
automation script *within* their game, and we do not break the competitive integrity
and the profit of DelightWorks/TM's service / game.
I'd like to think about it this way - we're hardcore enough that we need to consume/play everything in this game,
thus we're more likely to gacha more as a *whale* player.
It's a win-win condition as long as this script do not jeopardize competitive integrity,
which I don't think FGO will implement in the near future.)