There's some stellar libraries in Go for terminal stuff, in particular anything from charmcli. They have an elm style TUI framework called bubbletea (which superfile uses), a styling library, prebuilt components, it's really incredible. I'm building a multiplayer tetris you can play through ssh, which is using bubbletea and another lib of theirs called wish.
they have a lot of stuff you can just use in regular shell stuff too: https://charm.sh
In fact, their license page makes it abundantly clear they are not open source:
> We own and reserve rights to our content, including text, images, and code in the app, which is protected by copyright and other laws.
I get this argument if a company or product claimed it was open source and it wasn’t, but it just doesn’t work if the product in question makes it quite clear they are not, or even leaves it ambiguous.
> And are you suggesting that people normally click the license page?
As my comment says, I am suggesting that they explicitly say they are not open source. It’s not like that’s featured front and center on literally any other product’s front page, so I’m not sure what exactly your expectations are here. Do you want them to have in 100pt font “WE ARE CLOSED SOURCE!!!” plastered across every page? Would that be enough?