Undoubtedly. However many of the works posted on this site are by living authors with publishing contracts, such as Dave Hunt, Josh McDowell, Norman Geisler and John MacArthur, not to mention deceased authors who still have open copyrights such as Loraine Boettner and J. Vernon McGee. The copyright on Walter Martin's book was recently renewed with the Ravi Zacharias Edition.
This site apparently "Acknowledges" the copyrights, but does not claim permission to post them nor do many of these works contain the publisher's copyright notices.
While it would be nice if the publishers granted permission to post these works on-line, I suspect that they did not. I hope I am wrong, as this site contains many works which would be valuable, but I really do believe that many of these works are not being posted legally.
Seeing that the OP of this thread does not actually quote any of the works, but only links to them, no harm, no foul.