How does licensing work for open source software(available on the internet) or books written

Lets say i write a blog/book and reference for e.g. exact testcase used in the below blog.
https://antognini.ch/2019/04/vsql_cs_histograms-what-are-the-buckets-thresholds/

Or is that a strict no-no? Does every piece of blog/book have to be written by myself or does it depend on the flexibility or license details put by the author of the referenced blog/blook?

I plan put the reference details at the end of the blog/book.

another example.
i plan to use few of the scripts from the below: https://antognini.ch/downloads/top2/allfiles.zip

Some of the blogs/book refer to http://www.apache.org/licenses/LICENSE-2.0 What does it mean in simple terms. This is my first time so wondering and any inputs would be appreciated :)

Apologies if this is a very basic qn, but none of my peers/seniors have written a book and i have great regard for community here , so though of checking.

P.S. My above example is just one out of many i may use. I use many such on my day-to-day work

-- 
Cheers,
Kunwar

--
http://www.freelists.org/webpage/oracle-l