For those who use Jdowloader a lot and are tired of been alert for the captcha entry dialog, there is a free service that works with most download servers, its called CaptchaTrader.

You install the Jdownloader plugin so CaptchaTrader resolves the captchas for you, but at a cost. Not real money however, you just need to fill some captchas manually in the website from time to time to have some credits, those credits will be your coin that will use CaptchaTrader to resolve your captchas automatically

For more information about installation and use, refer to CaptchaTrader website.