Gligli is working to add support for JTAG/Homebrew Jasper 360s to libXenon, a library for writing programs for the Xbox 360 with XeLL, without using any existing code as a basis.
GliGli reports on logic-sunrise.com he managed to run a demo written with libXenon on a JTAGged 360 with Jasper motherboard.
There's still lots of work to be done, but once finished all JTAGable 360s will be compatible with the legal and open-source library. He hopes it will motivate more developers with write homebrew 360 programs using this legal alternative to the MS XeDK.