When using the command GET DOCUMENT PROPERTIES, the locked parameter returns a boolean value regarding whether the file is in read-only mode. One clarification is that MacOS calls this attribute as "locked" while Windows calls it "read-only" as shown below.

MacOS:


Windows:


This command should not be used to check whether a file has alread been opened in another application this scenario does not pertain to the "read-only / locked" file property. Instead, consider using OPEN DOCUMENT and catch the error to check when the file is already in use by another app.