It was created many decades ago and it buried the limitations of proprietary software, fostering the open collaboration of participants to create a useful worldwide product.
Usually, it enables the use of the source code and its design and content documents for the
end users or companies to change it if they so require to build their own product version
with the general restriction that the software origin be adhered to.
The business model of those companies set up with Open Source is based on value added
for that business, offering professional services, solutions, training and consulting services
for the software.