Kernel source code is now available for the GT-I9500, GT-I9505, and SGH-I337M
GPL compliance is a wonderful thing -- Samsung has just posted the kernel source code for three Galaxy S4 models: GT-I9500, GT-I9505, and SGH-I337M. All three sources are currently available for download through the Samsung open source repository. While this doesn't help the average user (plus nobody actually has the phone yet), it will allow kernel developers to begin tweaking Samsung's kernel in order to get flashable zips ready for root users once the phone launches.
The Galaxy S family has been huge with the aftermarket developer community in the past, and despite some initial bad news, there is no reason that the Galaxy S4 can't reach the same level of support and popularity among ROM and kernel devs. It will be interesting to see how far this powerhouse of a phone will be pushed. The links to the source code can be found below.