I think the issue is that MSI requires GNU bison to build. And so they are trying to figure out whether to: A.force developers to download GNU bison B.include GNU bison in the tree somehow as a binary file or something or C.check the files generated by GNU bison into CVS.
And also they are trying to figure out how to make sure that when someone changes the bison files or the .c files generated from them, the changes are copied upstream to WINEHQ and not lost.