The source code for firmware 2.3.2 (stora_source_2.3.2.tar.bz2) is a 460 MB download and can be found on the Netgear Readynas FTP site.
MacWire (Bryan McGuire) has created a github repository with Stora source code in an effort to use a more up to date kernel than the one used in the Netgear source code. This source is used elsewhere in this Wiki in Compile the kernel and Kernel Compile Howto
The GPL source code (425MB) can be downloaded from Seagate site.