I realized that www.freecodecamp.org and http://forum.freecodecamp.org are not using the same account, I must use different account/passcode to login, why this happens, why not just use ONE universal login?
You can login using GitHub in both, the main site and the forum.
The forum appears to be using forum software called Discource. Not sure what the rest of the site uses, but they are effectively two separate applications. They could share accounts, but it would be additional work to make that happen.
Technically we could write a discourse plugin but it’s not a priority. If you make a plugin that does this you could always ask here. freeCodeCamp and Discouse are both open source so you might be able to make a plugin with technical knowledge.
GitHub logins for the main site are only available to older accounts.
When beta ships, it will be handled with passwordless authentication.