The QuantLib project (https://www.quantlib.org) is aimed at providing a comprehensive software framework for quantitative finance. QuantLib is a free/open-source library for modeling, trading, and risk management in real-life.
QuantLib is Non-Copylefted Free Software and OSI Certified Open Source Software.
QuantLib can be downloaded from https://www.quantlib.org/download.shtml; installation instructions are available at https://www.quantlib.org/install.shtml for most platforms.
Documentation for the usage and the design of the QuantLib library is available from https://www.quantlib.org/docs.shtml.
A list of changes for each past versions of the library can be browsed at https://www.quantlib.org/reference/history.html.
The preferred channel for questions (and the one with the largest audience) is the quantlib-users mailing list. Instructions for subscribing are at https://www.quantlib.org/mailinglists.shtml.
Bugs can be reported as a GitHub issue at https://github.com/lballabio/QuantLib/issues; if you have a patch available, you can open a pull request instead (see "Contributing" below).
Contributions are very welcome! Details are in CONTRIBUTING.md