Download:

GSubEdit stable releases can be downloaded from GSubEdit's download page at sourceforge.
The changelog for version 0.4 is:

Improvements

• Added spellcheck support
• Added "Join file" action
• Added a "Subtitle info" box in the main window
• Swedish, Czech, Russian and Romanian translation included

Bug fixes

• Various bugfixes...

CVS:

The source in the CVS will always contain the latest version of gsubedit. However it is not recommended for non-experienced users to use it since it will contain bugs.
But if you consider yourself experienced, simply follow these instructions:

First you have to use ssh to communicate with the cvsserver: export CVS_RSH=ssh
Then enter the following from the terminal:

cvs -d:pserver:anonymous@cvs.gsubedit.sourceforge.net:/cvsroot/gsubedit login

When prompted for a password, simply hit enter.
After you've logged on, enter:

cvs -z3 -d:pserver:anonymous@cvs.gsubedit.sourceforge.net:/cvsroot/gsubedit co gsubedit

Now it should download the entire source into a new directory named 'gsubedit'

You can also browse CVS tree through sourceforge's web interface: here