I agree in thinking that a "port" is an insane idea. After all, given how quickly Calibre is updated, do you realise that after 3 years you will now be 3 years behind in the features Calibre offers? I seriously doubt any users out there will want an alternative inevitably bug-ridden version that attempts to offer the exact same functionality they got 3 years ago from Calibre? Without the huge user support base, community added plugins etc? So it would be purely for your own "benefit" in terms of coding knowledge, however as others have said there are alternative ways to do that.
By all means create your own book management application such as andyh2000 suggested above, people have different needs and certainly a "simpler" version of Calibre with far less features aimed at end-users who are less technical could be one such market. However I think you are crazy to spend 3 years full-time trying to emulate exactly an existing application...
But hey, it's your life, good luck!
