As @micaksica has said Rails is generally a pretty good framework and I've build and contributed to several projects myself and most of them I've never had any problems with.

If the developers put the projects together properly, it should have been very legible and easy to jump in on. Ruby isn't exactly a hard language to learn and generally very legible, almost to the point where each function/statement should be close to reading plain English (other than regexp and a few other things). That is, if the developers are following best practices, separation of roles, and not trying to hack together various work arounds because they don't know the language.