gf does not provide everything, its main focus is on graphics. Here is a list of recommanded C++ libraries that can be used:

Threading

• No need for an external thread library, C++11 provides threads, mutexes, condition variables and futures.

Network

• Asio or Boost.Asio: This library will be integrated in the future C++ standard, so it can be used safely if you want a future-proof networking library (Boost Software License).
• ENet: It's a reliable UDP networking library used in the game industry (MIT licence).

Audio

• SFML Audio: This part of SFML is independent and can be used without the rest of SFML, it is a simple abstraction above OpenAL (zlib/libpng license).
• PortAudio: This library is a low-level audio I/O library (MIT license).
• SoLoud: This library if an easy to use audio engine for games (zlib/libpng license).

Physics

• Box2D: This library is a 2D physics engine for games (zlib/libpng license).