public:

   explicit CleanUpDirectory(const KUrl &directory, const qint64 maximumSpaceUsed);

This should be the only constructor.

If someone really needs to pass a QString, he can use CleanUpDirectory(KUrl(string)). This stresses the fact that he actually should have used KUrl in the first place.

public:

  KFileItemList entriesToSort;

To be consistent, add m_

void CleanUpDirectory::deleteLeastUsed()

    if ( m_spaceCurrentlyUsed - spaceCleaned > m_maximumSpaceUsed ) {

This "if" has Space inside the braces. Since this is all new code, the coding style should be consistent. Since there are other style inconsistencies, I suggest to run it through astyle-kdelibs, which can be found in kdesdk/scripts.

#include <KJob>

#include <KDE/KJob> etc.

DirectoryUsageNotifier::DirectoryUsageNotifier( QObject* parent )

    kDebug(7020) << "constructed with = " << dirs[0].mPath << "to check every "

My "kdebugdialog" says that 7020 is used for "kded4", you either need a different ID, or switch to dynamic IDs.

Name[es]=Notificador de excesivo tamaño de directorio

It's nice that you want to help translating, but those translations are deleted on next scripty run :) Remove translations.

            <default>2</default>

If the default is to check every 2 minutes, then this is way too often. I cannot recommend a good default, but having my system cause disk contention by scanning for directory space usage every two minutes is inacceptable.

      <string> MiB</string>

Is there a way to get the localized/customized suffix? I have my KDE set to "MB".

      <string>&lt;!DOCTYPE HTML PUBLIC &quot;-//W3C//DTD HTML 4.0//EN&quot; &quot;http://www.w3.org/TR/REC-html40/strict.dtd&quot;&gt;

Please don't use HTML strings here. It specifies a fixed font and is horrible for translators. It is okey to add simple formatting using <qt> <br> <b> etc.