I remember back in the day this automated downloader program… the links had a limit of one download at a time and you had to solve a captcha to start each download.

So the downloader had built in “solve other’s captcha” system, where you could build up credit.

So when you had say 20 links to download you spent some minutes solving other’s captchas and get some credit, then the program would use that crowdsourcing to solve yours as they popped up.