Open-source refers to something that people can modify and share because its design is publicly accessible. Open-source methodologies have contributed to the growth and maturation of modern technology perhaps more than any other set of methodologies. They allow for anyone to contribute their specialties, grow their own ideas into businesses, write academic papers, find mentors, fix issues, etc. with a low barrier to entry for participation.
Feel free to use any open-source ICON products that you can find to learn, start a business, or share with others.
It may be useful to take some time to learn about software licenses so that you can know how open-source authors intend for their work to be used and so you can abide by any legal rules that they may be applying.