Linux – a linux cli equivalent to mac’s “open” command? or windows “start” command

It sounds like rsync is definitely what you are after. You do not need to set up an 'rsync server' to copy files from one machine to another. Rsync supports copying files over SFTP (SSH File Transfer) which most linux boxes have enabled already (if not manually disabled).

See Lifehacker's Mirror files across systems with rsync for more details:

Whether you want to backup your data, distribute files securely or mirror your working documents over the internet from the office to home, between computers on your local network, or from your computer to your web server, rsync can get the job done. Today we'll use rsync to mirror folders between a Mac and PC over a secure connection at the command line.

Rsync is free (as in speech) and cross platform, meaning it syncs files between operating systems (Windows/Cygwin, Mac OS, Linux); it works over ssh so it's encrypted and secure; unlike FTP it's incremental, so only the parts of changed files are transferred, not whole files, which makes it go like Speedy Gonzalez; and the fact that it's command line makes it scriptable and easily automated.

xdg-open is what you're looking for.

You might like this snippet I put in my .bashrc files so that whether I'm using cygwin on windows, linux, or OSX, I can use either the start or the open commands and they work great:

case "$OSTYPE" in
   cygwin*)
      alias open="cmd /c start"
      ;;
   linux*)
      alias start="xdg-open"
      alias open="xdg-open"
      ;;
   darwin*)
      alias start="open"
      ;;
esac

Good comments, xdg-open is indeed a better option than gnome-open as explained below. I updated my personal scripts a while ago, but forgot to update this answer.

WARNING: This will override the functionality of both openvt (virtual terminal) and start from init.