If you only had 90 seconds to explain what is open source, here is what you could say:
BTW: this artwork is licensed under creative commons with cc.ascribe.io. Creative Commons France inaugurated the launch of the new website with a new tool that unlocks the value of the bitcoin blockchain for the benefit of the Free Culture movement. ascribe enables creators to share their CC-licensed work without worry of loss of attribution. So this tool supports copyleft through the Blockchain.