gfortran is not g95 (for more detail about that see this). gfortran is available here.

A Debian version is available for testing here

GFortran is included in Debian testing and unstable in the gfortran package. This package will install binaries in /usr/bin.

t was simple to install on ubuntu:

[dkg@metis ~]$ sudo apt-get install gfortran{,-doc}
Reading package lists... Done
Building dependency tree... Done
The following extra packages will be installed:
  gfortran-4.0 gfortran-4.0-doc libgfortran0 libgfortran0-dev libgmp3c2 libgmpxx3
The following NEW packages will be installed:
  gfortran gfortran-4.0 gfortran-4.0-doc gfortran-doc libgfortran0 libgfortran0-dev libgmp3c2 libgmpxx3
0 upgraded, 8 newly installed, 0 to remove and 0 not upgraded.
Need to get 104kB/3148kB of archives.
After unpacking 7963kB of additional disk space will be used.
Do you want to continue [Y/n]? 
Get:1 http://us.archive.ubuntu.com breezy/universe gfortran-4.0-doc 4.0.1-4ubuntu9 [104kB]
Get:2 http://us.archive.ubuntu.com breezy/universe gfortran-doc 4.0.1-3 [798B]
Fetched 104kB in 0s (121kB/s)

Preconfiguring packages ...
Selecting previously deselected package libgfortran0.
(Reading database ... 65024 files and directories currently installed.)
Unpacking libgfortran0 (from .../libgfortran0_4.0.1-4ubuntu9_i386.deb) ...
Selecting previously deselected package libgfortran0-dev.
Unpacking libgfortran0-dev (from .../libgfortran0-dev_4.0.1-4ubuntu9_i386.deb) ...
Selecting previously deselected package libgmpxx3.
Unpacking libgmpxx3 (from .../libgmpxx3_4.1.4-10ubuntu1_i386.deb) ...
Selecting previously deselected package libgmp3c2.
Unpacking libgmp3c2 (from .../libgmp3c2_4.1.4-10ubuntu1_i386.deb) ...
Selecting previously deselected package gfortran-4.0.
Unpacking gfortran-4.0 (from .../gfortran-4.0_4.0.1-4ubuntu9_i386.deb) ...
Selecting previously deselected package gfortran.
Unpacking gfortran (from .../gfortran_4.0.1-3_i386.deb) ...
Selecting previously deselected package gfortran-4.0-doc.
Unpacking gfortran-4.0-doc (from .../gfortran-4.0-doc_4.0.1-4ubuntu9_all.deb) ...
Selecting previously deselected package gfortran-doc.
Unpacking gfortran-doc (from .../gfortran-doc_4.0.1-3_i386.deb) ...
Setting up libgfortran0 (4.0.1-4ubuntu9) ...

Setting up libgfortran0-dev (4.0.1-4ubuntu9) ...
Setting up gfortran-4.0-doc (4.0.1-4ubuntu9) ...

Setting up gfortran-doc (4.0.1-3) ...
Setting up libgmp3c2 (4.1.4-10ubuntu1) ...

Setting up libgmpxx3 (4.1.4-10ubuntu1) ...

Setting up gfortran-4.0 (4.0.1-4ubuntu9) ...
Setting up gfortran (4.0.1-3) ...

[dkg@metis ~]$