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 Downloads; installation instructions are available at Installation instructions for most platforms.
Find documentation for the usage and the design of the QuantLib library here.
A list of changes for each past versions of the library can be browsed at History.
The preferred channel for questions (and the one with the largest audience) is the quantlib-users mailing list. Instructions for subscribing are at Mailing Lists.
Bugs can be reported as a GitHub issue at 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