IFC++ is an open source IFC implementation for C++. It was originally developed at the Bauhaus University Weimar.
The project is published under the MIT license, which means that you can use it for any purpose, personal or commercial. There is no obligation to publish your source code.
Additional information as well as download links to the viewer application is on this project website: http://www.ifcquery.com
https://github.com/ifcquery/ifcplusplus/wiki/Build-instructions
980 000 entities loaded, 8000 with geometric representation. Loaded in < 4 sec. on a standard PC, including geometry.