I'm disappointed by this too. The FTC fined Peak Brain Training competitor Lumosity $2 million because it "deceived customers about the cognitive and health benefits of its apps and online products."[1] I was more hopeful about the app if it was standalone.

As for the code being open sourced, the results of the research should be publicly available but the material of the research is an asset of the university (like how the computers and beakers used in other experiments wouldn't be given away to the public). Commercialization of research ("tech transfer") involves additional costs and risks that are taken on by research institutions, researchers, and private entities. This PR announcement was likely not coincidentally following the release of the app to the public. There was likely additional costs outside of the original scope of research to make the app robust for public usage outside of the experiment setting.

Personally, I'm disappointed that something that sounds promising may not have a chance to stand on its own as an example of a viable application when other "brain training" apps have shown their more akin to placebos rather.

    [1] https://www.statnews.com/2016/01/05/brain-training-lumosity/