Hi @kyle forster ,
To add to Marcin's answer, you can qualify for the developer program by having a qualifying Visual Studio subscription type, being an ISV Success partner, getting added to the subscription by following the Microsoft AI Cloud Partner Program, or going through the new validation process in the page linked by Marcin.
In order to sign in, you need to use the Microsoft account or Microsoft Entra-enabled email, and you can change the primary email to associate with your membership.
See the FAQ.