just to clarify: you want the descriptive flexfield segment to be read-only, to only display data? For all users?
Fusion Apps Developer Relations
If you are asking whether you can make a descriptive flexfield segment be read-only (uneditable), then the answer is yes.
See Table 4-1 in Task: Define Attribute Properties in Using Flexfields for Custom Attributes - 11g Release 7 (11.1.7)
That table lists the ways in which you can configure a segment.
The Read-only checkbox is in the Display Properties section in the Edit Segment page of Manage Descriptive Flexfields.