Hi F1R0Z! your post I was very useful for me to install arduino ide in N900 thnx! so now i will try to help you with upload code..

i did it just 5 min ago.. via bluetooth so after arduino ide i installed bluez in debian chroot (just apt-get install bluetooth..) i paired n900 with the HC-05 module connected with arduino (you can find some tutorial for this ) after that i opened the com port rfcom0

to find the ip adress : hcitool scan

sudo rfcomm bind /dev/rfcomm0 xx:xx:xx:xx:xx

launch arduino ide and you can find the port frcom0