Nice project, I like what you did!
I would like to use Unofficial OpenGL SDK as an external git submodule of a small project I am starting to experiment with OpenGL ( https://github.com/SRombauts/unofficial-opengl-sdk). Thus, by not using the Zip package you release, I have to execute get_externals.lua manually to get the 4 external library.
So I had to install lua (premake4 embed lua but does not provide a general interpreter, or did I miss the point ?)
Second problem : require("ex") require "ufs"
I did not manage to find those 2 extensions ; - Ubuntu 12.10 does not seem to provide adequate packages. - LuaForWindows only provide "ex" and searching "lua ufs" in Google only brings your own get_externals script...
So, here are my questions ; 1) why using non standard lua extensions ? 2) if more common lua is not appropriate, why using Lu's in the first place (I understand that premake uses lua, but for an entirely different job) Basic Python would do it far easier. 3) why not using a mercurial feature to manage those 'subrepository' (http://mercurial.selenic.com/wiki/Subrepository : metcurial can manage SVN externals) ? 4) or, at the root of the problem, why not embedding as well those 4 external library directly into your repository?
Solution 3 is my favorite; indeed it's what I am trying to achieve with my own projects!
I could offer some help for this task if you want.