...Prism describes itself as an organization to "protect the quality of scientific research", which it hopes to do by opposing policies "that threaten to introduce undue government intervention in science and scholarly publishing." What policies are they opposed to? Why, this one, which recommends that NIH-funded research results be freely available to the public when they are published.
In short, they want to protect science by locking it up under copyright. They want to restrict access to publicly-funded research results by requiring that everyone pay a fee to see it. There are plenty of reasons why PRISM's logic falls apart (see here for a thorough bashing), but I wanted to point out just one: they're hypocritical. While their entire web site advocates strict enforcement of copyright laws, the images they've used on their front page are a violation of copyright law. Take a look at this screenshot from their front page: [PS: omitting image.]
Notice how the hairdo of the handsome scientist in the large photo is marred by the "Getty Images" logo? That's a digital water mark that stock photo suppliers use to keep unscrupulous publishers from "borrowing" their images. A quick search of the Getty Images web site locates the identical photo, with the identical watermark: [PS: omitting image.]
Clearly PRISM was too cheap, or in too much of a hurry, to bother with copyright (if you look closely at the other two photos, you'll see watermarks on them as well).
However, they're happy to make it expensive and inconvenient for taxpayers to access the research they've paid for.
[Update: Looks like they've now replaced the watermarked images with paid versions. Apparently facing a Slashdot avalanche was enough to set them straight. But the point still holds: Dealing with copyright and DRM is expensive and inconvenient, and taxpayers who've already paid for research once shouldn't have to pay again to see the results.]