The disk-space check from the Qt5.0.0 installer seems to check only the available space on the '/'-partition, instead of using the partition on which its supposed to be installed. In my case df -sh shows this:
Filesystem Size Used Avail Use% Mounted on rootfs 1008M 191M 767M 20% / udev 10M 0 10M 0% /dev tmpfs 406M 584K 405M 1% /run /dev/disk/by-uuid/20a684e3-2ac8-47bf-a5c3-bd8f38a6ee10 1008M 191M 767M 20% / tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 1.8G 464K 1.8G 1% /run/shm /dev/mapper/vg01-lvhome 146G 78G 61G 57% /home /dev/mapper/vg01-lvtmp 2.0G 68M 1.9G 4% /tmp
And I took the default installation directory of $HOME/Qt5.0.0, yet the installer claims there are only 766.2 MB of free space available and does not let me continue.
Used 'Packaging' component as it was required and I didn't see an Installer component anywhere.