Commons Content Party

That's not at odds with the manifesto:

Copyright protection should last only as long as necessary to achieve a reasonable compromise between protecting and rewarding the author for his intellectual labour and safeguarding the public interest in the dissemination of culture and knowledge

This is more about reminding people that the default state of things is public domain. Copyright isn't a natural right, it's a government-granted artificial monopoly for the purpose of incentivizing new works, just as you want to do. It's good that it helps provide you with an income, but shouldn't be confused with a natural right.

For example, Sonny Bono wanted copyright to last forever:

Mary Bono, speaking on the floor of the United States House of Representatives, said:

Actually, Sonny wanted the term of copyright protection to last forever. I am informed by staff that such a change would violate the Constitution. ... As you know, there is also [then-MPAA president] Jack Valenti's proposal for term to last forever less one day. Perhaps the Committee may look at that next Congress.

This is pushing back against that way of thinking, and clarifying what the default is.