ChaiScript
Embedded Scripting Language Designed for C++
... is fully tested for 32bit and 64bit on Windows (MSVC2013), clang++ and g++. ChaiScript has been making stable releases since 2009. No bug fix or feature is made without a corresponding unit test. By default ChaiScript is thread-safe. Thread safety can be disabled for enhanced performance. ChaiScript is licensed with the BSD license and is free to use in your free or commercial projects.