I can see your concern, however edamame is considered the immature soybean. Overall the issue with Soy is due to the processed foods that are made with them as well as soybean oils etc. The edamame eaten in such a small portion should not an issue to anyone. As with all foods there are good and bad things associated with them, you just have to consider what is best for yourself. If you would like to avoid them due to the GMO factor that is understandable, however for some people this is a huge step up from adding other processed junk to their diet.
Here is an article you might find interesting:
It points out some good information as well as the bad points.
Great question, overall just use in moderation if you do like edamame,but like anything else too much of a good thing can be bad.
Have a great day!