Yes, it’s true that open source projects that cannot pay to license content owned by other people are at a disadvantage versus those who can. Open source projects cannot, for example, wholly copy code owned by other people.

Also, beware of originalist interpretations of the Constitution. I believe there’s been about 250 years of law clarifying how copyright works, and, not to beat a dead horse, I don’t think it carves out a special exception for open source projects.