These are experimental 64bit binaries. For completeness, 32bit binaries built using the same method are also included. The libraries in these packages are made using GCC (MinGW) toolchain. It is presently not possible to use these libraries with any recent version of the Microsoft Visual C compiler because of conflicting C-runtimes. To help you resist the temptation, the import libraries (.LIB) are not provided at all. If you need these libraries in an environment which mandates the use of the Microsoft toolchain, you will have to build them from source yourself.