I do not think that there is any registration fee. you have to select places which you'd like to travel to in exchange of offering:
1. any skill
3. helping in an sustainable project.
also, you offer your skill for making more facilities available which varies from places to places. You may get free tour for one location in exchange of offering a skill or so but for other location, yo may not have option of free tours. basically, you get to have facilities if you are ready to offer any of those 3 things mentioned above as well.