If there's the need to upload really large files – 5Gb – in a 32bits OS, eZ will load the whole file into the memory which then will be exceeded.

This is probably the bad line:

kernel/private/classes/clusterfilehandlers/dfsbackends/dfs.php (115)
$ret=$this->createFile($dstFilePath,file_get_contents($srcFilePath),true);

the INT limit of a 32bit system will be simply exceeded.

The idea would be, to use a functionality using the copy command instead. this command doesn't really need a lot buffer.