As far as I know, we cannot localize the file upload dialog box. It
is a client call and its language depends on the language of the OS on
the client side.
If you just wish to change the language on the click button, you can
- <div mce_keep="true">make a button (for instance an input; it doesn't even have to run at server)</div>
- <div mce_keep="true">the 'Open File'-dialog is opened by pressing on a button you can modify any way you want.</div>
- <div mce_keep="true">Hide the fileInput control</div>
to make a file upload control yourself.
The only way to change the file open dialog box is to construct an
ActiveX control of your own to do this.