> it sounds like you some-what 'ported' bundler to dart...
More or less. Most of pub's code is devoted to stuff that's specific to Dart, but it's underlying "philosophy" is Bundler's model.
> what's your impression of how difficult it would be extend a tool like this to work for many languages?
This comes up a lot, but my hunch is that we're unlikely to see a successful language-agnostic package manager. The package manager has to be written in some language, and users of language X generally don't want to be told that they have to install language Y before they can download packages for X.
Also, most of the code for a package manager is fiddly details related to the specific language in question. Thinks like how files are organized, running tests, etc. The amount of code you could share is actually pretty small.