Most Linux developers I have encountered, use all their software for free.

As a computer professional, I install the RedHat 7.2 or 7.3 Linux operating system and utilities onto a customer's computer(s) free of charge anyway.

May I charge for software that I develop using C++ or Python and Qt/X11 Free Edition?

May I make customers pay fair price for transfer/license of the computer professional's intellectual property, personal labor and operational costs incurred (salaries, rents, electricity, air-conditioning, etc.) not to mention profits/margins.

Does developing software using a Free or Open Source software development environment, prevent/preclude me from legally selling (charging for), application programs and reusable components developed by me, without giving away the source code?

What is our position with: copyleft, Free/Open Source, etc.?

Ram