Deep Thought writes "Texas Instruments, already infamous thanks to the signing key controversy last year, is trying a new trick to lock down its graphing calculators, this time directed toward its newest TI-Nspire line. The TI-Nspires were already the most controlled of TI's various calculator models, and no third-party development of any kind (except for its very limited form of TI-BASIC) was allowed until the release of the independent tool Ndless. Since its release, TI has been determined to prevent the large calculator programming community from using it. Its latest released operating system for the Nspire family (version 2.1) now prevents the calculators from downgrading to OS 1.1, needed to run Ndless. This is TI's second major attack on Ndless, as the company has already demanded that websites posting the required OS 1.1 remove it from public download [PDF, in French], obviously to prevent use of the tool. Once again, TI is preventing calculator hobbyists from running their own software on calculators they bought and paid for."