Gimme a minute… it looks like code changes in PR #41 somehow got into master…
@sonko, I’ve looked through the master branch, and do not see any references to the core package (phew… you had me worried!). Maybe you downloaded some/all from this branch, which renames the openhab package to core? Stick with the master branch for now, and you can use this for the startup delay script, which is also included in PR 41 (a major overhaul). If you are still having issues, just let me know (preferably in a different thread), and I’ll help get you started with JSR223-Jython!
PS, I’ll add a comment to the docs in regards to setting permissions on /etc/default/openhab2.