It seems to reject an absolute wrong and right, and in fact the article mentions how its contents are subject to change... but beyond that I'm not sure what to make of it.
It does reject an absolute right and wrong, and wisely so in my opinion.
What is derived from need and interest is not derived on a whim. The rest of the manifesto sets the context. We need food, water, and shelter, and our interests are comfort, love, power and success(plus a few more). What the surrounding context means is that any otherwise negative interest (power) must work within the manifesto - work to benefit society and be concerned for the well-being of all. It definitely doesn't mean that might equals right, which is apparent in the later paragraphs.
If our moral systems were truly absolute, tied to something objective and unchanging over time, we'd still be stoning people to death outside the front gates for adultery. We'd still have slaves, and atheists would be shunned from society as evil. Even in religions where morality is supposedly absolute, it changes with the times.