When opening a read-only project, a dialog is prompted informing the user that the project is read-only and offering to save it elsewhere. On BlueJ 4.1.2, this appears as:
The project being opened is read only:
To use this project, you will need to choose a new location to save it to.
The colons on the lines before and after the project path are not supposed to be visible (they are in the labels file to prevent the blank line causing a label to end, but are supposed to be removed before display, as in previous versions).