Look at Lua (www.lua.org) a very simple (seeming) scripting
language that is dead simple to extend, also is free and has a very
liberal license.  The manual is quite short and the language is roughly
similar to Pascal.  You can have someone doing scripts very quickly but
the language has all the support for objects, structures and other
support for quite complex programming.  The language is written in very
portable C and comes as source (just type make). I have not had
problems building it on Linux, Solaris,OS X  or embedded systems, they
have done an execllent job of making is very compliant and easy to
compile.

    In addition if you need some special functions, it is very very
simple to add new classes for say hardware or some special software
function.

   If you are ever tempted to put scripting into a program, run don't
walk to www.lua.org and use it.  The language can either be the outside
controller or embedded into a program as the script engine.  They do
all the stuff you need and many things you haven't thought of yet.  As
an example see the terminal server for OS X (TCP/IP <-> serial port
connector) that is scripted in Lua.
(http://members.bellatlantic.net/~vze35xda/Load/TERMS.zip) In this case
Lua is the script engine inside the program.

    There is also an execllent book written by the authors of the
language (Programming in Lua by Roberto Ierusalimschy).
(http://www.amazon.com/gp/product/8590379817/002-5881463-0072035?v=gla...)