High Quality Content by WIKIPEDIA articles! The STLSoft C++ Libraries are a collection of open source C++ template libraries that extend the functionality of the Standard Template Library (STL) and provide facades that wrap operating-system and technology-specific APIs. STLSoft is licensed under a BSD-form license which allows it to be used with both open and closed source projects. STLSoft aims their library to be lightweight and having high portability, high performance, minimal coupling and high cohesion.