Hi Ghuron! You have specified https://dspull.github.io/ as the callback URL for DSPull. AFAIK github.io only hosts static webpages; you cannot do OAuth securely with a static web page (there is no way to keep the secret key secret) so they are not allowed (see the last bullet point on OAuth_app_guidelines#Developer_guidelines).
Also, an app that allows editing protected pages (which means significant vandalism potential) should ideally be hosted on Toolforge so there's a better audit trail. --Tgr (WMF) (talk) 09:42, 19 July 2019 (UTC)