(disclaimer: I worked for Molecular Systems Biology)
The last issue of PLoS Biology caries an editorial about Open Access written by Catriona J. MacCallum. It addresses the definition of Open Access and what the author considers an "insidious" trend of obscuring "the true meaning of open access by confusing it with free access".
I agree with the main point of the editorial, that we should keep in mind the definition of open access and that the capacity to re-use a published work should have more value to the readers.
However, it is very unfortunate that the very fist example MacCallum picks on is the Molecular Systems Biology journal for the simple fact that very recently they have changed the publishing policies to address exactly this issue. Authors can choose one of two CC licenses, deciding for themselves if they want to allow derivatives of their work or not. See post at MSB blog. As it is explained in the blog post the discussions about the licenses actually started several month ago and I think the final implementation is a very balanced decision on their part.
Thomas Lemberger, editor at MSB wrote a reply to the editorial that PLoS decided to publish as a response from the readers. These can only be seen if readers decide to click the link "Read Other Responses" on the right side of the online version.
I am obviously biased but for me this is not really giving the right to equivalent response. It would not have cost them much to issue a correction or publish the letter as correspondence where it would have the same visibility as the editorial. This would signal that they are indeed committed to collaborating with other publishers and journals that support open access (as stated in PLoS core principles).