The Wikimedia Incubator is the normal Incubator, but the policy of the Wikimedia Incubator does not allow test languages without a valid ISO-639 code. We think that's unfair. We want to give all languages a chance to develop a Wikipedia, Wiktionary or whatsoever. The creators of the Incubator Plus wanted to have a safe place for test languages. We want to guarantee safety for your test at the Incubator Plus. Of course there can always be vandalism, but we hope to reverse vandalism as quickly as possible.