Perl 6 and Parrot Essentials is now open source.
A long time ago in a galaxy far, far away, Allison Randal, Dan Sugalski, and Leo Tötsch wrote Perl 6 Essentials , which later became Perl 6 and Parrot Essentials . The universe has changed quite a bit since then. Despite that, the first chapter is still very interesting because it's a slice of history about what people were thinking and why things happened the way they did.
Allison recently arranged for O'Reilly Media to transfer the rights to The Perl Foundation so it could potentially turn into a community work that is up-to-date and relevant. The source files are currently marked as copyright of The Perl Foundation, but I suspect that will morph into something community-oriented. Allison told me that it's really under Artistic License 2, and that should work for now.
The Perl 6 parts of the book went in the Perl 6 source repository, which you can access with SVN (and probably a few other ways). This command just pulls the source for the book. You can back up as much as you like to get more of the repository:
$ svn co http://svn.perl.org/perl6/doc/trunk/books/tutorial
The parrot parts of the book are in their own section in the parrot repository:
$ svn co https://svn.perl.org/parrot/trunk/docs/book
The source is the Pod export from O'Reilly's internal format, and you can use Allison's Pod::PseudoPod module to deal with it (which is, by the way, what I used for Mastering Perl , so the tools I use to make the Mastering Perl website would work here too, and all of that is in the repository listed on that site).