I would like to find someone who would proof-read a Press Kit of an Mac OS X app in exchange for a license. Do you know any website / service where I could find some English native speaker, ideally technical writer, who would be interested in an offer like this?
If you offer a free license, I would ask people you know directly. Easier and more promising than online.
Sites taking licenses as payment do not exist as far as I know. But there are free services out there. Maybe you want to check them:
I haven't tested any of them. Also take a look at the Startups StackExchange site.