SPContentType.ReadOnly property
SharePoint 2013
Gets or sets whether the content type is read-only.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
Marking a content type as read-only warns users that they should not make changes to the content type. The user must then explicitly set the read-only property of the content type to false to make changes to the content type.
For more information, see Content Type Change Control.
If you define a content type as read-only, that can have ramifications when you make changes to its parent content type and then attempt to propagate those changes down through the hierarchy. For more information, see Updating Child Content Types.