Okay here the results of a short investigation:
As you already know csync2 does not want to be installed using apt-get, the reason for this (as far as I can see) is that the debian people made a mistake in the dependencies of the libgnutls26 package. It states on a package line that it will break csync2 versions lower or equal then 1.34-2.2, which is odd because the version provided IS version 1.34-2.2, I guess the error is that the 'break' rule of the package should state versions LOWER then 1.34-2.2 and not LOWER OR EQUAL then version 1.34-2.2
What does it help to know this: NOTHING.
But there is a way to get csync2 installed anyway, here is how:
first we're only going in download the package using:
sudo apt-get download csync2
After running this command the package (csync2_1.34-2.2_armhf.deb) should be as a file in the directory you started the command in.
After that I needed to install using the normal way two additional packages:
sudo apt-get install librsync1
sudo apt-get install sqlite
And for a final working version you'll also need one of these installed:
openbsd-inetd OR inet-superserver
Now for the csync2 part, we're going to use this command to install it:
sudo dpkg --install csync2_1.34-2.2_armhf.deb
It will complain about the same stuff as apt-get did before, but it will install it anyway. One latest check to see if all library requirements are met:
should output something like:
libgnutls-openssl.so.27 => /usr/lib/arm-linux-gnueabihf/libgnutls-openssl.so.27 (0x400a3000)
libsqlite.so.0 => /usr/lib/libsqlite.so.0 (0x400b4000)
librsync.so.1 => /usr/lib/arm-linux-gnueabihf/librsync.so.1 (0x40081000)
libgnutls.so.26 => /usr/lib/arm-linux-gnueabihf/libgnutls.so.26 (0x4010b000)
libtasn1.so.3 => /usr/lib/arm-linux-gnueabihf/libtasn1.so.3 (0x4027e000)
libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0x40294000)
libp11-kit.so.0 => /usr/lib/arm-linux-gnueabihf/libp11-kit.so.0 (0x401c6000)
/lib/arm-linux-gnueabihf/ld-linux.so.3 => /lib/ld-linux-armhf.so.3 (0x40009000)
libpthread.so.0 => /lib/arm-linux-gnueabihf/libpthread.so.0 (0x401dd000)
libgcc_s.so.1 => /lib/arm-linux-gnueabihf/libgcc_s.so.1 (0x401fc000)
libgcrypt.so.11 => /lib/arm-linux-gnueabihf/libgcrypt.so.11 (0x403c3000)
libz.so.1 => /lib/arm-linux-gnueabihf/libz.so.1 (0x40038000)
libdl.so.2 => /lib/arm-linux-gnueabihf/libdl.so.2 (0x40056000)
libgpg-error.so.0 => /lib/arm-linux-gnueabihf/libgpg-error.so.0 (0x40072000)
In the output shown above there should be no, 'File not Found' Errors, if there are you need to install those libs using the normal apt-get way.
Now you have a (as far as I can see) working version on csync2 on your RPi. starting csync2 does result in a help screen and not some coredump, error or otherwise not working thing, so I guess it is now a matter of configuring it and done...