Does this work with Webform 4.x?

Bump. I guess with no maintainers, maybe not. Have you tried an install? See what happens?

I installed webform_registration on webform 4.X
It works, still creating new account, assigning role, showing confirmation page, etc...
I'm still having a "Notice: Undefined property: stdClass::$webform_registration in webform_registration_inc_form_alter() (line 21 of \sites\all\modules\webform_registration\webform_registration.inc)."

I think it could be related to https://www.drupal.org/node/1336486

Unfortunately the module cover a quite specific case and maybe there are not people interested enough to get involved. By myself I'm not good enough to handle this

I am getting a similar message too on latest webform 7.4x (also using webform_localization module) - the user is created and logged in but I get the following:

Notice: Undefined index: administer_users in user_register_submit() (line 3894 of /home/xxxx/modules/user/user.module).
Notice: Undefined index: und in webform_registration_inc_form_alter() (line 61 of /home/xxxx/sites/all/modules/webform_registration/webform_registration.inc).

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This is a shame as its a very useful module... Unfortunately I dont have the skills to be able to provide a patch or fix...