Openplanet 1.24.4 will include a new feature: Developer Mode. When this option is enabled (either through the Developer menu or by enabling it on startup through the settings), you can run unsigned plugins (if you have Club Edition). When it is not enabled, you can only run signed plugins, which should be practically (almost) all plugins in the plugin manager.
By default, the option is disabled. That means that only signed (and trusted) plugins will be loaded by Openplanet. This allows dedicated community competition hosters to limit in which capacity players with Openplanet can play on their competition servers. This is (currently) done through a
[DEVMODE] tag added to Openplanet's system information. We've worked closely with the Evo team to collaborate on this feature, including an implementation for EvoSC servers. (In the future, we hope to add more control for dedicated servers as well.)
If your plugin is currently uploaded unsigned on the plugin manager and you would like for it to be signed, please upload a new version to your plugin admin page and mark that you want it to be signed.