I dunno... I've used an open-source license for IntelliJ in the past, and that took a lot more work than just sending an email. (Kudos, btw, to JetBrains for their great open-source licensing program!)

It's probably less work for me to send an email explaining why I think I deserve a free account than to tell the system to send emails to five email addresses that route to me, and then do whatever I need to do to validate them.