This software is in the grey area of legally accepted conduct,
Indeed it is - similar services are already employed by the criminal underground, and usually used for things like registering free email accounts for the purpose of spamming.
I'm not sure I like the idea of making a tool like this public - as an individual, you really don't spend that much energy on solving a captcha every now and then. Ah well, if you awarded credits can only be used for solving other captchas and there's no dollar-payout, it might not be
that bad.