If you guys like Lua have you checked out Squirrel? It's like Lua, but with imperative (C) style syntax.
http://squirrel-lang.org/
Has:
Open Source zlib/libpng licence
dynamic typing
delegation
classes & inheritance
higher order functions
generators
cooperative threads(coroutines)
tail recursion
exception handling
automatic memory management (CPU bursts free; mixed approach ref counting/GC)
weak references
both compiler and virtual machine fit together in about 6k lines of C++ code.
optional 16bits characters strings
compiles on both 32 and 64 bits architectures