Thanks for all the good words:)
As for your questions, yep, the package contains the raw source code. To get all the files just like you mentioned (tests, grunt etc.) you need to buy the license, log in to your account and download it via Bower or SSH.
If you have any custom plugins, they should work automatically. Download the package, copy your plugins to the proper directory and build it. Let us know if something wrong pops up!