I think this is really dangerous. It adds magic to bash scripts, which then makes them really difficult for new users to read and debug. If you like concepts from Java and JavaScript, why not just write shell scripts using a different language altogether? What's the benefit of using bash at all?
This kind of thing is done in other languages all the time, but shell scripts are often doing things that are very important not to screw up.
There's no magic here. The code is quite clear, if you wish to review. Moreover, each module is independent, so you can include only the files that you find useful, after reviewing them beforehand.
As to why:
1. For fun, as an exercise.
2. It does make it more pleasant to write and debug readable Bash scripts.
Obviously — you should always use common sense and choose the programming language to your needs.
What exactly do you mean by this? I would love to have a real language in bash scripts but the examples here do not appeal to me because of the O-O semantics. A simpler language would be nice.
This kind of thing is done in other languages all the time, but shell scripts are often doing things that are very important not to screw up.