I no longer use GitHub for original projects. Source for fftool isn't public yet but I understand the concern — running an unaudited binary is a real ask. My site leans toward educational, so that people consider building the tool from the instructions in the article. I may host the source on the site as a zip or tarball at some point so people can more easily build it.

As for Linux API - TIOCGWINSZ via syscall.IOCTL to get terminal dimensions.

Why Linux and Go - Linux is the only OS I use. I like Go because it produces a single static binary with no runtime dependencies. Thanks for your interest.