As of yesterday OAPEN has a new URL path for its record-pages and PDFs, with (it seems) no re-directs. The URL paths have been updated in JURN, but they are not yet known to Google Search — and thus JURN is temporarily without OAPEN results.
They are generally quite verbose in terms of spawning pages that show up in Google Search, but not as horribly verbose as DOAB. Thus, while not perfect, OAPEN is found in JURN and not the DOAB.