Since Build16 Widelands has a built in LUA interpreter for campaigns and tutorial missions. The goal of this blueprint to develop a flexible framework for scripting the current and future computer players (AIs) for widelands.
A good example for this is OpenTTD, only they use Squirrel instead of LUA: http://wiki.openttd.org/AI:Main_Page
Note from Nasenbaer 2011-09-28
I discussed this feature with SirVer some months ago and we unfortunally came to the point, that Lua Scripting is to slow and takes too much CPU resources. This should not be understand as general "blocker" for this feature, just as note, that it would be prefareable to write all CPU intensive functions in c++ and only use LUA to define the "main loop" of each computer player.