IMHO, in terms of legality, as long as you're not using his book(s) for your own commercial purposes, there's nothing inherently wrong or unlawful about quoting excerpts from his book by posting on the Forum in trying to help or respond to someone's question, e.g., "The answer to your question, O.P., is to place the ……… in line with the …….. and use 14 gauge …….., per the DCS Companion 3rd Edition at page ……. by Barry Broskowitz, which states, ..………….".
His books are in the public forum and there's nothing illegal about quoting from his books anymore than quoting something from a movie or record or other book in the public forum.
In order to avoid plagerism, you should always make an attribution as to where the information you're giving originally came from, as in the above example and you certainly want to insure that you are not mis-quoting something.
