NLM is pretty clearly not public domain; Copyright Information & Downloading National Library of Medicine Data, for example, says:
Prospective licensees and those considering downloading data for redistribution should obtain opinion from legal counsel for any use planned for the author-generated abstracts in National Library of Medicine (NLM) databases and to ensure compliance with intellectual property laws. NLM cannot provide advice about copyright issues. Some material in the NLM databases is from copyrighted publications of the respective copyright claimants. Users of the NLM databases are solely responsible for compliance with any copyright restrictions and are referred to the publication data appearing in the bibliographic citations, as well as to the copyright notices appearing in the original publications, all of which are hereby incorporated by reference. Those who search NLM databases may download for personal use and may provide others with a single copy of downloaded data.
DanConnolly (talk) 23:15, 30 March 2010 (UTC)
"Government information at NLM Web sites is in the public domain. Public domain information may be freely distributed and copied, but it is requested that in any subsequent use the National Library of Medicine (NLM) be given appropriate acknowledgement. When using NLM Web sites, you may encounter documents, illustrations, photographs, or other information resources contributed or licensed by private individuals, companies, or organizations that may be protected by U.S. and foreign copyright laws. Transmission or reproduction of protected items beyond that allowed by fair use as defined in the copyright laws requires the written permission of the copyright owners. Specific NLM Web sites containing protected information provide additional notification of conditions associated with its use."