Thank you everyone for your input. I have decided to declined the contract offer after indirectly checking with my HR. I was told that I can't work to someone else at the same time which I have committed for my employer. If I want, I may work after regular office hours if there is no conflict of interest
@sql: I see what you mean but would not be applicable in my case. As I mentioned, I referred one of my friend and he has been working with one of the renowned org and still did not get selected due to the lack of current market's trending tech stack though he is excellent resource and learning new thing and working on it is nothing for him. Most of the companies who hires contractor expects you to pick up the things quickly unlike permanent role where you would be given sometime to learn