All you have to do is set 4 options in DJ-Classifieds options, on tab 'Global'
1. In 'General Settings' section set parameter Access level to 'All users'.
2. If you want to allow unregistered users not only to post ads but also to edit their ads please set parameter 'Guest can edit ad' to 'Yes'. If you allow unregistered users to edit their ads, the email with unique edition link will be sent after posting an ad. This will allow unregistered users to post ads.
3. In 'Advert Specific Settings' section set parameter 'Email fo guests to 'Yes' or 'Yes-required'. This way unregistered user will be asked about his email while posting an ad.
4. If you want to allow unregistered user to edit his ads please set parameter
New ad email to user to Yes in section Notifications Settings.
If the user who has posted ads as unregistered decides to register, his previous ads can be automatically assigned to his new account (if he uses the same email address). To achieve this you need to install and enable DJ Classifieds User Token Adverts plugin.