Depends on what you mean by trust. This wasn't made any clearer by reading the article.
"We promise not to do bad things" is not a safe long term contract. If they can change the terms at any moment and retain control, then they can break that promise and that's final.
This is why open source matters. This is why we shouldn't let people try to change the meaning open source. True open source is forever open, it is the author's Ulysses pact.
FUTO keyboard is source available, and that's final, too. Whether it is also "source first" and if that term is worth recognizing at all is a separate and entirely valid discussion. Even the worst incarnation of source available is still generally better than closed source, in my mind.
Can there be a trusted space between open and closed source? Maybe, I don't see why not. Again, define trust, and who's judging. Some people already trust closed source proprietary software, for some reason, while others strongly reject anything that isn't free software—remember, we're not talking about price, here.
I wish FUTO and Rossman all the best, as I do with the free software ecosystem and most of open source. Open source is open source, though, let's not get it twisted.