I have read in various documentation that when Vim is started in Ex mode, it attempts to "act like" Ex, so I gather from this that Ex is a separate program and is not an actual part of the Vim source code and has its own separate code maintained by people other than those maintaining Vim. If this is true, what is the relationship between the two?
Does Vim copy and paste Ex's source code into its own project to create the Ex functionality, or does it try to emulate it from scratch?
I notice that the regular expression syntax and features in Ex and Vim appear to be identical. If they are completely separate programs, then how is the parity maintained? Do they have a shared regex library that both use?