Of course, you can open any program from a shell.
That would actually be a nice improvement, but since the tool is at the EOL anyway and there's like me and 1 other person using it, I don't think it's worth spending more time on it.

GU Decks is very slow, but this is purely from a page loading perspective. Opening a link from a terminal window is the same speed for both links. On the other hand, sometimes the more compact way GU Decks presents decklists is more convenient.