Yes, you can do a lot of those things, but over homebrew. You can install ipkg-opt, which will give you access to the nslu2-linux optware packages. It's no apt, but you can still use it to install packages. From the optware packages, you can install python/ruby/php, install a vnc server (although I think there are some homebrew apps for that), install git, cron, and a lot of the standard programs you would expect in a standard linux installation.
I'm not sure on ssh port tunneling/forwarding, but curl/wget come installed on webOS.
WebOS is looking really good. Can anyone point me to an architecture diagram along the lines of [1]? The best one I could find was [2], which doesnmt give many details.
Tunneling has worked like a champ for me. With a linux box at home and a linux phone in my pocket, corporate blockers are a thing of the past and all of my work is only ever an ssh away. =]
I'm not sure on ssh port tunneling/forwarding, but curl/wget come installed on webOS.