Tiago Forte has been working on these ideas for many years in the open on his blog (Fortelabs, the one OP posted) and Building a Second Brain is the course he built atop that. From what I have seen of it, its original work and some synthesis of past ideas, just like most things.

It's weird to see you do these quick Google searches and speculate its plagiarized without any substance to back your argument or awareness of the work he's been doing for years now.