It is possible to extract the source code from the MikroElektronika mikroC libraries as sets of C source code file. But they have made the process complicated.
From my view, if you are smart enough to find a way to extract the library source code you are smart enough to write better code using a better development environment. If you cannot find the way then you still need microC to hold your hand. Don't get me wrong, microC is very useful to help develop skills for embedded application code development.
My quibble with the mikroC Integrated Development Environment(IDE) is that once your use their libraries in a project it is almost too much work to port that project to a different class of controller (PIC16 to PIC18 or PIC24) , or an IDE like MPLABX with XC8 or XC16.
MikroElektronika deserves to get paid for all their efforts to make the IDE and compilers available. For me what they offer is not worth the price. Your resources and needs will be different.