2.5.2 is a new bugfix release. It includes substantial changes to the new Qt client. See the full list of changes.
Source code is available in the usual place. Compiled Windows packages aren't available yet, but should follow shortly; we'll post again here when they turn up.
Stable release 2.5.2
Re: Stable release 2.5.2
Windows builds are now up.
Re: Stable release 2.5.2
I found out that Ubuntu Software Center still installing 2.4.2-1 version of Freeciv, instead of latest stable one (2.5.2). I tried to reach them, but with no effect. Could someone email them? After all, Freeciv is one of most notable games for Linux!
Re: Stable release 2.5.2
The packages in an Ubuntu release are frozen in time (I infer that you're using Ubuntu Trusty from 2014). You probably want to investigate requesting a backport; see the bottom of the UbuntuBackports page (there is no existing Freeciv backport for Trusty).