is it completely legal to use light weight java game library in a commercial 2 dimension game engine like drag and drop not straight code?if yes what are their requirements?if not what are my options? thanks in advance.
I am not a copyright lawyer. This answer is based on a layman interpretation of the license text and on common practices in the software development industry. When you want to be sure, ask a real lawyer.
It is a weak copyleft license. That means you can use it in any program published under any license. The only condition is that you include the license text with the disclaimer in your product. Contrary to strong copyleft licenses like the GNU GPL this does not imply that the license conditions apply to your own work. They only apply to the LWJGL components. Your own work is still licensed under your license terms.
The usual way to do this with tools is by integrating it into your about dialog and also put it as a text file into the program directory. The usual way to do this with games is by putting it into the credits roll.
Also, you are not allowed to use the LWJGL name to endorse or promote your product. So you can not use advertisement slogans like "Jawad 2d Game Engine powered by LWJGL".
When the games created by your game engine also depend on LWJGL, then your users are also obligated to add the LWJGL license text to their games. You might want to do this automatically when building projects.