I'm using the last beta 1.6 with PostgreSQL 8.1
Because it is not an interactive enrolment plugin. The per-course enrolment option is for when you allow students to trigger their own enrolment, examples:
- manual enrolment ("Want to enrol in this course now? [yes/no]" with the option of using course keys)
- paypal ("want to enrol? pay here!")
- OSCommerce ("want to enrol? pay here!")
The other enrolment plugins (ldap, db) check your enrolment against an external data store -- probably with data from a SIS. This will work regardless of the course->enrol setting.
Does that help?
Is it possible to test your OsCommerce approach/interoperation with Moodle?
Looking forward to it
If you are impatient and happy to figure things out, the custom OSC package is at http://git.catalyst.net.nz/gitweb?p=oscommerce.git;a=shortlog;h=mdl-osc-ceed -- use the 'snapshot' link.