The IUOMA is free for all members because of the many sponsors that donate to the IUOMA or because of the IUOMA bookshop that brings in money to keep this platform alive & free.

you can visit the bookshop at:

http://www.lulu.com/spotlight/iuoma

and when you order a few books, a small fee will be going to the IUOMA and you will get some lovely books on Mail-Art.