Good things first: Using the KDE Partition Manager version from svn is safe.
There hasn't been any substantial development work being done on KDE Partition Manager for quite some time. This is indeed very deplorable and mostly owed to the fact that I am so far the only developer working on the project. The time I was able to devote to open source work has been severely limited over the last couple of months due to, as they say, circumstances beyond my control.
So the project has remained in a rather dormant state since my series of blog entries about the upcoming featurs in version 1.1 and the post about the new partition widget design that had been so magnificiently done by Hugo.
As an aside, this design has again been improved quite a bit after that post, so here's a current KDE Partition Manager screenshot (also, everyone likes screenshots):
Meanwhile, the GNU Parted devs have released a new version of libparted, 3.0, that does away with its former support for resizing FAT-based file systems (and a few other special cases that libparted used to cover for historical reasons). This version is now the only one shipping with a few distributions, among them Gentoo.
In KDE's subversion, I have at one point last year actually added support for the new libparted 3.0 version to KDE Partition Manager (support being an euphemism for: remove FAT16 and FAT32 resizing and a few other things when building against libparted 3.0). Gentoo have then proceeded to ship (as much as Gentoo can be said to ship anything) an svn-snapshot of KDE Partition Manager that has the version number 1.0.60 (denominating it as an alpha release in KDE's version number scheme). Other distributions have followed or will probably do so in the near future.
Now using a subversion snapshot for an application that is supposed to perform potentially destructive actions on your important data sounds like an unwise choice, does it not?
To put it briefly: Version 1.0.60 is no more dangerous to your data than 1.0.3 is. The code involved performing the potentially hazardous actions is mature and thoroughly tested. There's no guarantee in either versions and there have indeed been modifications to code areas that deal with moving data within file systems for 1.0.60, but it's not like this has all been rewritten from scratch with totally unexplored code-paths now being let out into the wild sans any prior testing. The code works, is safe and I have used it numerous times myself on my disks, not just for testing.
Making backups before touching your file systems with any tool is still the diligent thing to do.
If and when KDE Partition Manager will see a 1.1 release is still not certain; I'm trying to figure out what I can do to accelerate matters a bit.
tl;dr Using KDE Partition Manager from subversion (with a version number of 1.0.60 or higher) is no more dangerous to your data than using 1.0.x.