That's what is it about:
A proposed legislation would require final manuscripts of peer-reviewed journal articles based on federally-funded research to be made freely available on government-hosted websites six months after publication by commercial and non-profit publishers (such as the AAA).
The AAA does not like this and joined 65 other disciplinary associations and small publishers etc and protested against this legislation.
Here are their main concerns about the legislation, expressed in a letter by these associations:
1) it would undermine the value-added investments made by publishers in the peer review process;
2) it would duplicate existing mechanisms that enable the public to access scientific journals by requiring the government to establish and maintain costly digital repositories;
3) it would position the government as a competitor to independent publishers, posing a disincentive for them to sustain investment and innovation in disseminating authoritative research. The net result, opponents argue, is that the overall quality of research competitiveness would be lowered.
The AAA is mainly concerned about "the potential impact the proposed legislation may have on the AnthroSource business model and revenue generation".
Three excellent comments on this issue:
Bryan McKay: Will AnthroSource go open source? (Les Faits de la Fiction)
Kerim Friedman: Open Source Anthropology (Concerns over the ethical dilemmas involved in producing knowledge about the “other” have, in the past few decades, radically changed how anthropologists conduct research and write ethnographies. Unfortunately, they have not changed how we publish).