Prusa Slicer was forked from Slic3r. That's kind of the point of free software; fork it, change the colors, stick your name on it. (Prusa has done a lot more than that, of course.)
Frankly, the less software that hardware companies write, the better. They already have their hands full with the firmware and probably don't need to be setting up CI infrastructure for Linux/Mac/Windows and all that stuff.
