Why does gnu.org flymake documentation is for version 0.3, but elpa.gnu.org has version 1.0.8 available?

Question

I have Emacs 26.1 installed. It has a built-in package flymake version 0.3. Also, googling flymake gives me https://www.gnu.org/software/emacs/manual/html_mono/flymake.html as the second link in the search output. It looks like the main and the most official documentation of flymake on the internet. It says "This manual is for GNU Flymake (version 0.3, April 2004)".

At the same time on https://elpa.gnu.org/packages/flymake.html there is a version 1.0.8 of flymake available. It looks less like a site with official information about GNU projects, but still it's hosted on the gnu.org domain. So, my questions are:

1. Why is the most official looking documentation of flymake about such an old version?
2. Are these actually the same packages?
3. Is the package https://elpa.gnu.org/packages/flymake.html supported by GNU or is it a third party package?

Answer 1

Packages on ELPA are supported by GNU, and that version of flymake is clearly marked as an official part of Emacs (check the header of flymake.el).

Flymake 0.3 is the version that ships as part of Emacs. Version 1.08 is a newer version of the same package available from Elpa.

So, to answer your questions:

1. The official documentation refers to an old version of the package, because that package is still the version installed by default. I don't know why, perhaps there are backward-incompatible changes in the newer version?

2. They are different versions of the same package, apparently maintained by the same people, or at least the same group.

3. Flymake on ELPA is officially part of Emacs. (as is the older version 0.3)

This same situation occurs for AucTeX and Org-mode. I think it may be because development on those packages is faster, with more frequent releases, than releases of Emacs itself. So the default installed packages are quickly out of date, and having a more recent version in Elpa allows users to keep up to date.