I have seen some few syllabuses online that look very similar. Is it fine to adopt any syllabus or instructors need to have their own syllabus? And do instructors need to get permission from the original syllabus writer or just link and acknowledgement?
In some cases, it could be that the instructors had a template provided by the school. When I was an instructor at a college, I was required to update a few things on the syllabus, like my name, but I was required to NOT change ANYTHING else. I had no flexibility (in that one specific way... I did have a whole lot of flexibility with just about every other way that I ran my particular class, which I know is quite different than what some other instructors experience). One thing I did have the flexibility to do was to create my own addition to the syllabus, but the college bureaucracy, which determined the official course objectives, also mandated a certain amount of information get presented unaltered.
In that case, I, as the instructor, never bothered to check the copyright of each and every syllabus, because obviously I had the organization's permission to do what the organization absolutely required of me.
This is just one example: The main point being, in some cases, instructors might not be creating their syllabus entirely from scratch. Surely, the specific details vary from school to school.
It's probably a (morally) minor copyright violation in the US to just copy the material and use it. At the very least, you'd want to borrow that material with written (email is fine) permission from the original writer. You can't simply acknowledge your way out of copyright infringement. IANAL, but there are those who might argue in the US that the collection of what you will teach in what order when is not sufficiently creative enough to warrant copyright protection (it's already that way for recipes), but that's an argument for a court to hear not a way to rationalize your own behavior.
On top of this, there's probably local things required by your university or government that will be specific to you that will need changing anyway, so unless you are borrowing last year's instructor's syllabus from your own university, you're presumably going to want to do more than just copy someone else's.