Is Groovy the most native scripting language for OH?

Setup, Configuration and Use Scripts & Rules
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As a side note, for Groovy⇔openHAB-Automation users JSR223: Update Groovy example by dilyanpalauzov · Pull Request #2720 · openhab/openhab-docs · GitHub suggests concise way to utilize SimpleRule:

import org.openhab.core.automation.*
import org.openhab.core.automation.module.script.rulesupport.shared.simple.*
import org.openhab.core.config.core.Configuration

scriptExtension.importPreset("RuleSupport")

automationManager.addRule(new SimpleRule() {
    {
        name = "Main"
        description = "Primary Logic"
        uid = "1-2-3"
        tags = ["T"]
        triggers = [
            TriggerBuilder.create()
                .withId("aTimerTrigger")
                .withTypeUID("timer.GenericCronTrigger")
                .withConfiguration(new Configuration([cronExpression: "0 * * * * ?"]))
                .build()
        ]
    }
    Object execute(Action module, Map<String, ?> inputs) {
        org.slf4j.LoggerFactory.getLogger("A").error("Hello World from Groovy")
    }
})