[rer]

Sentences are creations. Does this mean every sentence we write on HN or say to each other by default is closed and needs a license?

[gus_massa]

Actually yes, but so most sites has some legalese in the TOS and there is also fair use.

IANAL. TINLA. You can probably quote a comment from one HN user, but if you copy all the comments from one "famous" user of HN and write a book with them, then you'll probably get some copyright problems.

[volaski]

Nope, your sentences are not as valuable as you think. Neither is mine. But a great book containing thousands of sentences is valuable enough to to be purchased.