I need to understand rules that I only read but never understood completely. I'm asking here some clarifications. I read that GPLv2 licence imposes that a developer, developing a software using codes with GPLv2 licenses, must release it with the same GPLv2 licence.
Imagine a user asks a developer to create a software for a system (machine) using different licence types. What type of licence will have the developed codes?
Moreover, if the developer uses just some libraries with GPLv2 licences, is he obliged to make public the whole code for this system? And what about, if the user wants to sell several of these systems? Should the developer release the code mandatory or can he release only the executable?
I know that a software with a GPLv2 licence running on a OS, does not oblige that OS to be with GPLv2 licence. But what about if I create a SaaS using software with GPLv2 licence? Also all the software developed to make my Saas on the server has to be with a GPLv2 licence? For example, I know https://www.rollapp.com/ that make a lot of GPLv2 applications run directly on the browser. Are these guys obliged to make their code with GPLv2 licence.
What about the last two concerns, but with another type of licence, like MIT licence, or BSD?
Anyway, could you suggest a method on how to manage all these type of information when you face different libraries with different licences?