The job-dsl run-condition-plugin support is incomplete as AlwaysRun and NeverRun are not supported by SimpleCondition. At present javaposse.jobdsl.dsl.helpers.step.condition.SimpleCondition assumes that condition classes end in Condition. However the AlwaysRun and NeverRun conditions do not require the Condition suffix.

Existing code
String getConditionClass() {
"org.jenkins_ci.plugins.run_condition.${subPackage}.${name}Condition"
}

One possible solution
String getConditionClass() {
if (name.endsWith("Run")) {
return "org.jenkins_ci.plugins.run_condition.${subPackage}.${name}"
}
else {
return "org.jenkins_ci.plugins.run_condition.${subPackage}.${name}Condition"
}
}