Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
MIT License - A license from the Massachusetts Institute of Technology.
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.
Simplified BSD License - Also known as the "2-clause" BSD license, this is a simplified version of an open source license created at the University of California Berkley.
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .
GPLv2 - Created for the GNU project, the GNU General Public License version 2 is the most popular free software license.