A correspondent writes to ask about the sentence The meeting ended inconclusive, which he says he has seen in newspaper report headlines. He also points to Christoph Loreck's book Endymion and the Labyrinthian Path to Eminence in Art, which contains the sentence The foreword ends inconclusive. But 'should this be inconclusively?', he asks.
Standard English usage after end is adverbial, so it would normally be inconclusively. I've seen the adjective used in news reports too - a Google search suggests that these are mainly from South Asian publications, so it might be a feature of Indian English. Replacing an adverb by an adjective is also a common interference pattern from some other languages. A German-speaking character in the film The Third Man advises Holly Martins to 'go careful' in Vienna. Perhaps this is the source of Loreck's preference, for he is German. And the vacillation turns up in some English dialects as well, for all kinds of reasons, and these will gradually influence informal standard English. For instance, ease of articulation motivates they lived happy ever after instead of the standard they lived happily ever after.
Why has the adjectival usage arisen at all? One possibility is ellipsis: the speaker is thinking of the sentence as short for something like 'The meeting ended with everyone inconclusive'. But I think it more likely that the verb is being influenced by the very similar verb end up, which readily takes an adjective: We ended up happy. The similarity in meaning can be seen from such examples as The day started sad and ended sad and I didn't know whether to be happy because the series ended happy or to be sad because the series ended. It's all very interesting, albeit somewhat inconclusive.