You can override login and register result page for OAuth by copy everything (except this file) in this folder into wp-content/themes/%your theme%/okv-oauth/templates

For example: If your current active theme is bootstrap-basic4 then you can copy everything here into wp-content/themes/bootstrap-basic4/okv-oauth/templates

Your folder structure will look like:
wp-content/themes/bootstrap-basic4/okv-oauth/templates/okv-oauth
wp-content/themes/bootstrap-basic4/okv-oauth/templates/okv-oauth/index_v.php
wp-content/themes/bootstrap-basic4/okv-oauth/templates/okv-oauth/register_v.php