I remember hearing that parts of Lightroom were written in Lua, but I didn't know that there was a publicly available SDK.
I am actually a programmer by trade, but C++ is my language of choice. I've never even heard of Lua except in relation to Lightroom, and know nothing about it. I've found some documentation at http://www.lua.org/manual/5.2/manual.html
The existence of the SDK does suggest a way to sychronize stacks between LR and Bridge, albeit an inelegant one. I could write a script to export Bridge stacks to a text file, and a LR script to parse the file and recreate the stacks. I know that the Bridge part is easy, but I don't know if the LR part is even possible. I'll need to have a look at the SDK.