There is no harm in asking if something is legal or illegal. That's the only way to find out something if you do not know. Since using a No-CD crack is considered piracy you will generally recieve a response of "don't do that" in this forum.
Interpreting the law is outside my jurisdiction (ha, ha... get it?). What you linked to is generally referred to as "Fair Use" which in a nutshell means if you buy something you have the right to make a copy of it and keep the copy as long as you can prove you own the original product. So if your game DVD gets damaged you will technically need to keep the damaged DVD in order to legally prove that you own the game. However, if you loose the game DVD, then that's a different story. You no longer possess the original game DVD, at that point your copy is now illegal.
You need to read the user terms of agreement that comes with games. It usually pops up when you install the game. Most people simply check off the "I have read this...." and click continue to install the game. That agreement will basically state that you do not have the right to by-pass the copy protection that comes along with the game.
This basically results in a "gray area" between the Copy Right law and the terms of the agreement that you agreed to in order to install the game. Since game publishers can generally afford to hire expensive lawyers compared to the average gamer, the net result is using a No-CD crack is in violation of the terms of agreement.