This page explains the current status of the translations in GnuCash. There is a separate introduction into Translation in general, but this page explains where you are invited to work on and where not.
See also http://lists.gnucash.org/pipermail/gnucash-devel/2009-January/024700.html but the branch names there are not any longer up to date.
Stable 2.6.x releases
As of January 2014, we are releasing 2.6.x versions regularly and they should now include the correct translation as well. The development of 2.6.x releases currently happens on the "trunk" branch, until we at some point will branch off a stable 2.6 branch but this is not the case in early 2014. Please update your translations on the "trunk" branch for subsequent 2.6.x releases.
There is no String Freeze active in 2014.
Again: Please work on the "master" branch of Git for your translation work, if you retrieve the code from the repository (which is highly recommended). Note that we are preparing to discontinue commits to subversion and make that repository read-only; it will very quickly become obsolete. The git repository is active and you should immediately delete your subversion repository if you have one.
No more gnucash-2.4.x
The development of the 2.4.x branch has ended in winter 2013 Gnucash-2.4.15 was (most probably) the last release of that branch. Please do not continue any translation work on the 2.4 branch of GnuCash!
No more gnucash-2.2.x
The development of the 2.2.x branch has ended in spring 2009! Gnucash-2.2.9 was the last release of that branch. Please do not continue any translation work on the 2.2 branch of GnuCash!
No more gnucash-2.0.x
The development of the 2.0.x branch has ended in spring 2007! Gnucash-2.0.5 was the last release of that branch. Please do not continue any translation work on the 2.0.x branch of GnuCash!
No more gnucash-1.8.x
The development of the 1.8.x branch has ended in fall 2005! gnucash-1.8.12 was the last release of that branch. Please do not continue any translation work on the 1.8.x branch of GnuCash!