I would like to start writing my portfolio to improve my probability to get a job as a developer. I know that I can do small problems on my own but there are also libraries I use. What kind of guidelines there are to post code on the Internet? I mean, if I write code that uses Pandas and Matplotlib, do I have to ask a permission for the authors of the libraries to use their functions on a program that will be on the Github as I finish the program? Or is there copyright issues if I write the code such that it has not used other code from the Internet but downloads a code from Github, writes another source file and then compile or run the code the other script made?