These are some TI-Nspire tools I [ExtendeD] have contributed to, mainly innovative proof-of-concepts, development utilities and low-level hacking.
Ndless combines since its proof-of-concept late 2009 [hackaday] [slashdot] a resident program and a GCC-based toolchain to open the TI-Nspire to third-party C and assembly (ARM) development, such as Mrakoplaz’s port of Doom [endagdet]. Some call it the TI-Nspire jailbreaker.
geogeo contributed to critical parts of the initial releases but unfortunately had to leave the team mid-2010. Ndless is today updated by a group of enthusiasts from TI-Planet.org and Ominimaga.org.
Luna is a Lua program to TNS document converter that can be used as an alternative to the official SDK. It defeats the compression and encryption layers required since OS v3.0.2. Cross-platform and command-line based, Luna streamlines your Lua build chain. It can also generate any TNS document from its XML source.
oclua is a proof-of-concept of a copy/paste-based on-calc Lua code editor.
HIDn is a set of Ndless-based USB mouse and keyboard drivers with native integration with the TI-Nspire OS.
OCD is an on-calc debugger that mirrors most of nspire_emu debugger’s commands. Add it to your toolbox for low-level hacking.
9sweeper was one of the first third-party Lua programs after Goplat’s discovery of a way to run them.
Nleash defeats the downgrade protection of the TI-Nspire OS v2.1.