Other ways to help
The project can be helped not only with code: bug reports, testing, translations and ideas.
Bug reports
Bugs are filed as issues. How to write a report is described in How to report a bug.
Testing new versions
Install new releases and check your own use cases. Leave feedback in issues or in the JournalPHP community.
Translations
Interface translations are in resources/lang/. How to improve a translation or add a language is described in Extending the code.
Ideas
Suggestions for the platform are welcome in GitHub Issues: describe the problem the feature should solve and the expected behavior.