I noticed it's been about 9 months since the above exchange, and was wondering if in that time you'd heard from anyone who's been able to make this work with SimpleNews.

I did take a look at the code because I was interested in trying to do that, but I'm not sure where to start - it seems to be designed to send the info to an outside site's API via SOAP, and I'm not sure how to pass that to another module internally instead. (I haven't really got any substantial experience in Drupal module development, though I've made a few tweaks to other people's modules here and there.)

I think it would basically need to pass the information to the simplenews_subscribe_user function in simplenews.module, only I'm not sure how to make it do that. The contact form when submitted just goes to itself, so it would have to call the other module in the background somehow rather than submitting the form to it directly, and I'm not sure how that would be done. Any ideas?