There is a class for plugins and themes that makes custom meta boxes easier to develop called cmb_Meta_Box from Custom-Metaboxes-and-Fields-for-WordPress at https://github.com/WebDevStudios/Custom-Metaboxes-and-Fields-for-WordPress and they update that class and code.
I'm trying to make sure that if I use the latest version of this class/script in a plugin that if a user has an older version of it, it fails gracefully. So, for example, 1.1.0 has some new features, but if someone already has loaded 0.9.0 from another plugin that loaded before my plugin, what can I do? There is now a constant so I'm thinking I could warn the user on my admin pages, but if they're not technical they wouldn't know what to do with that warning.
I hope this makes sense and some folks have ideas what I can do within WordPress to solve this possible issue.