Could a parrot build a spaceship? Evolutionary constraints on the language of a space-faring species

It is uncontroversial that a technological civilisation anywhere in the universe capable of building interplanetary transport must possess a form of language, so that complex cooperation between individuals is possible. However, the nature of ETI language (Extra Terrestrial Intelligence) is potentially very different from human language, both in its modality (e.g. acoustic, visual), and possibly also in its information encoding paradigm (e.g. words and sentences, grammar). If an alien species communicated with a very small repertoire of sounds, would it be incapable of developing sophisticated cooperative technology? Could such communication systems ever evolve to be true language? If physical constraints on the diversification of repertoire lead to the evolution of a low-vocabulary communication system, language may develop in unexpected directions, which would pose a problem for the identification and interpretation of ET signals.