"Work created before the existence of copyright and patent laws also form part of the public domain. The Bible and the inventions of Archimedes are in the public domain. However, copyright may exist in translations or new formulations of this work." [Wikipedia]As posted by Tony is the Chemical Abstract Service (CAS) discouraging using their CAS services for assigning correct CAS numbers to structures for any third party database. Wikipedia is a source of structures, which is public domain due to its GNU FDL. Still, this does not imply that any translation of structures, e.g. CAS numbers, are in the public domain, too. Honestly, this raises a serious problem for curating CAS numbers on Wikipedia and this raises indeed the question, if they should not be dropped from Wikipedia, and any other information source, at all? Is it not better having no information, than having wrong information?
A CAS number is for me only one certain translation of a chemical structure. In this case, the only source and creator for CAS numbers is the American Chemical Society. CAS claims that their services can not be used for curating other data sources. Does this also mean that people can not use CAS numbers from publications?
"The public domain can also be defined in contrast to trademarks. Names, logos, and other identifying marks used in commerce can be restricted as proprietary trademarks for a single business to use. Trademarks can be maintained indefinitely, but they can also lapse through disuse, negligence, or widespread misuse, and enter the public domain. It is possible, however, for a lapsed trademark to become proprietary again, leaving the public domain." [Wikipedia]And does this also mean that scientists are basically not allowed publishing CAS numbers and structures in scientific publications? How can CAS numbers then be used at all, if we can not store this information?
Many questions, and who will answer them? And, if they got answered what is the way forward for getting curated structures within the public domain? I would say (again, this time in nicer words): 'get organized scientists worldwide!' If CAS can do it, we can do it? It may take longer to get the party started, but if we do not start it will never happen.
"An ideal collaborative resource would be designed for large-scale data mining, contain curated historical data, and have data standards and deposition tools that could constantly bring in data from the published literature. ... In other words, the party might take longer to get started than hoped for, but it should be worth the wait." [M. Baker, DOI 10.1038/nrd2148]
Source: CAS numbers are not public domain, are they?