btOOL is a pair of libraries, one in C and one in Perl, that give programmers unhindered access to BibTeX files. The C library, btparse, is based on a lexical scanner and parser written with PCCTS, and also provides various string-processing functions necessary to emulate BibTeX. It would be a pain in the neck to write serious BibTeX tools in C, so I have also written Text::BibTeX, a Perl library that provides an object-oriented interface to BibTeX files and entries. In addition, Text::BibTeX includes a framework for writing Perl classes that do the job of BibTeX style files; the initial version of the Bib database structure---eventually meant to emulate the standard style files of BibTeX 0.99---is included as an example of using this framework.
Bibster is a Java-based system which assists researchers in managing, searching, and sharing bibliographic metadata (e.g. from BibTeX files) in a peer-to-peer network.