Obviously a 16:9 movie, or?
The Inspector indicates the file was encoded as a PAL anamorphic video. Whether the the original content is actually 4:3 or 16:9 will depend on how it looks when played in your multimedia player. Basically, PAL DV or DVD standard files are encoded using a 720x576 matrix whether the source content is 16:9 (1024x576) or 4:3 (768x576). Similarly, NTSC DV/DVD files are encoded using a 720x480 matrix for playback as 4:3 (640x480) or 16:9 (853.3x480) displays. In each case, a Pixel Aspect Ratio (PAR) is used to tell the media player how to display the file. For instance, QT 7 would display the file as a 1024x576 display assuming a 1:1 (square pixel) PAR value for the "Encoded/Normal/Current Size" setting while QT X would apply the embedded PAR value to the encoded 720 width to display same file at the same 1024x576. Thus, this file should play correctly whether it is being played in either an "old" or a "new" technology media player assuming the file is properly encoded for the source content.
iDVD says 4:3 to it.
Not knowing the specific work flow it is difficult to say what is going on. Generally speaking, the user determines whether an iDVD project will be 4:3 or 16:9 and in the PAL or NTSC standard when creating the the project. So, it is altogether possible to improperly encode content using the wrong standard/settings.
How to export from QT Player such a movie to get it broad 1:1 out from iDVD?
If by QT Player you are referring to the QT X Player, then you are stuck using the embedded PAR and available preset options. Using QT 7 Pro or the free MPEG Streamclip application you would simply set encode dimensions to equal the desired playback display dimensions. This will automatically set the PAR value to 1:1, as well as, set the "Encode/Normal/Current Size" values for proper playback in both "old" and "new" technology media players. This work flow requires the file data be re-compressed. If the ecoded height and target display height are the same, then alternative work flows are available to to reset the PAR and/or "Current Size" display values without having to re-encode the data. Specifics would depend on which values your wish to change and/or which applications/utilities you have at your disposal.
