Bio4j includes RefSeq data now !
A word about the RefSeq data (I haven’t reproduced all the hyperlinks, which are many):
NCBI’s Reference Sequence (RefSeq) database is a collection of taxonomically diverse, non-redundant and richly annotated sequences representing naturally occurring molecules of DNA, RNA, and protein. Included are sequences from plasmids, organelles, viruses, archaea, bacteria, and eukaryotes. Each RefSeq is constructed wholly from sequence data submitted to the International Nucleotide Sequence Database Collaboration (INSDC). Similar to a review article, a RefSeq is a synthesis of information integrated across multiple sources at a given time. RefSeqs provide a foundation for uniting sequence data with genetic and functional information. They are generated to provide reference standards for multiple purposes ranging from genome annotation to reporting locations of sequence variation in medical records. The RefSeq collection is available without restriction and can be retrieved in several different ways, such as by searching or by available links in NCBI resources, including PubMed, Nucleotide, Protein, Gene, and Map Viewer, searching with a sequence via BLAST, and downloading from the RefSeq FTP site.
BTW, note that the RefSeq information is stored in the Bio4J DB but the sequences are held as separate files on S3. See the blog post for details. (Thanks to @pablopareja for the correction on storage of refseq information in the Bio4J DB.)