Hi inkisiivi,
No, you can't connect the S900 to the internet.
You can connect it to your local WiFi network (by using the Yamaha USB WiFi adapter "UD-WL01"). This WiFi (Wireless LAN) connection can be used to install Expansion Packs from the YEM (Yamaha Expansion Manager) on the keyboard. You can also use the WiFi connection for MIDI.
Best regards,
Chris