There are some side effects that you should also consider when saving metadata to the images. However, some things like Collections are not saved even when using this option. This can be done on demand with a CMD-S (CTL-S) or automatically by turning on the 'Automatically write changes to XMP' option in the Metadata tab of the Catalog Settings dialog. So in order of other applications to be able to see that metadata it has to be explicitly written out to the image file or in the case of raw files to the XMP sidecar file. Other than the metadata (EXIF mostly) in the original image file, Lightroom by default keeps all its additional metadata (IPTC, keywords etc.) internally in it's own data base. If on the other hand you use Photo Supreme to only read the image metadata and print as you suggest it is possible but there are some things you need to aware of. You can easily get your metadata quite scrambled. However if Photo Supreme is trying to update the metadata within the actual image files on your hard drive you will want to be very careful with how you use Photo Supreme.

Basically there shouldn't be any problems running two database applications at the same time unless Photo Supreme is actually trying to read the Lightroom database.

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