Having spoken now to various teachers about online systems for university EFL postings I am leaning towards Moodle because it is a Course Management System rather than just a bulletin board, or a Content Management System like Joomla or TikiWiki.
I think that Wikis are too technically difficult for EFL students to use at less than advanced level - considering how much difficulty most native-English speaking, computer-literate students in FET 8611 are still having with kG use, I wouldn't consider this for use in Korea.
However, it seems that Moodle is coming up as a good candidate as I have spoken to 3 English teachers who use it successfully with Korean university students. There are no sign up problems reported like the awful mess I had with phpBB, and it is secure and reasonably stable. The only problem I have heard reported about Moodle was the board content suddenly disappeared mid -semester, and was only re-instated after the adminstrator updated to the latest version of Moodle. Something to watch out for, I guess. Also I heard that there is a steep learning curve to set it up for courses, but once it's up and running it's pretty easy to maintain.
So now that I am sure Moodle is free and suitable for use with Korean university students I feel more confident to go ahead and explore its application. I will have to change my Assignment 2 proposal though...and ditch phpBB. There's no point in putting any more energy into an insecure, redundant system that I have no intention of using again for classes.