Yes - this is because in the US, there’s a law called COPPA that makes it very complicated to allow services to collect any information about people under 13. So this applies to pretty much all websites and apps.
As @camperextraordinaire pointed out, the kids are welcome to use freeCodeCamp as long as they don’t create an account or submit any personal information. We don’t store any data from people who don’t create accounts. This said, 100% of freeCodeCamp’s challenges and content are available without needing to create an account.
I hope this is enough information, and that this doesn’t pose too much of an inconvenience for you and your learners.
Thanks for helping us spread word of the freeCodeCamp community, and for helping young people get interested in coding!