archlinux.orgは安全ですか？

This is the official website for Arch Linux, which is a Linux Operating System based on the principles of rolling release updates (meaning updates are released as they become available) and being bloat-free. Arch Linux is free open-source software and the operating system is continuously updated and there is no "Final Version".  Since it is based on being lightweight without included bloat it allows you to only install the software you want. While Arch Linux is a great Operating System, It will definitely be a learning curve if you are not use to Linux in general. Some Linux Distributions come prepackaged with Desktops and other software similar to how Windows is released... But with Arch Linux you start out with a command line and install everything you need from that point on. Arch Linux provides a well documented wiki that provides guides to help you get started. It has an active community that usually can walk you through things easily.

This Linux distribution is very fast and customizable. The software on the .iso images and packages in the official repository are safe, but be careful from installing from the Arch User Repository (AUR), in which someone might post a malicious build script. If you do install packages from AUR, make sure you read over the scripts to make sure there aren't any malicious commands.