I have a mac from 2006 and it is already not supported by new Apple system. So I did get back to Linux and I did chose Ubuntu 13.04. I did install Ubuntu side by side with OSX, but I did notice that Ubuntu did install itself on fat partition. Why Ubuntu uses fat partition? And can I change it to EXT4 without loosing already configured data?
Note: Originally posted as comment; re-entered as an answer, as suggested by Oyibo.
My suspicion is that Zagroda is seeing the EFI System Partition (ESP), which is FAT. Another possibility is that an OS X utility is reporting partition types based on their type codes; Ubuntu 13.04 still uses the same type code for its data partitions as Windows uses for FAT and NTFS. A fix to libparted has been in the works for two years, but the libparted developers have been sluggish in pushing it out. The output of both sudo parted /dev/sda print and sudo gdisk -l /dev/sda would be informative. (The latter will require installing the gdisk package.)