Sorry, I didn't explain myself properly.
When the program asks me to specify the folder containing the modules, I do so without problem (I actually clicked on the appropriate folder).
But at that time, the program tells me that this directory is not valid (see screenshot) and then endless loop (forced to kill it to get out of this loop).
I tried to indicate other folder, assuming I did not refer to the correct one, without better results.
So I searched the forum to see if others had the same difficulty and I found the 2 links (specified in the first post).
And also this one: http://www.juce.com/forum/topic/just-compiled-ubuntu-124-however-it-couldnt-recognize-module-folder
So I followed what did Jerome (on this post: http://www.juce.com/forum/topic/introjucer-cannot-find-modules) and found that I had error messages on the terminal.
Also Jerome said:
However it looks like the communication between IntroJucer and the native file picker window can be garbled by messages on, presumably, stderr.
So I fixed the cause of the messages, and IntroJucer magicly worked
If it's a similar problem, my question would be more: "Does anyone has an idea how to correct an error such as the one specified in the first post?"
Hence my suggestion: Perhaps missing some libraries?