Here's a short FAQ for those who want to try Punix on their calculator:
Q. Does Punix wipe the factory default OS?
A. Yes, Punix replaces the existing OS and all user files. However, you can download a new version of the TI-OS from http://education.ti.com if you decide to go back to the original OS.
Q. Which calculators does Punix run on?
A. Punix currently has the best support for the TI-92+, since that is the only TI-68k calculator that I own, but I will upload versions of Punix for the TI-92+, TI-89, TI-89 Titanium, and Voyage 200.
Q. Will Punix run on the TI-Nspire?
A. Nope. The TI-Nspire has completely different hardware than the TI-68k series. I don't have much interest in developing for the TI-Nspire anyway, so somebody else will have to port Punix, or maybe even a port of Linux, as the hardware seems to be capable of running Linux.
Q. How do I install Punix on a calculator?
A. You will first need to have a GraphLink cable (or a homemade variant) and TiLP installed on your computer. TI-Connect might work as an alternative to TiLP, but I've never used it so I can't say whether it works. Pull out one of the calculator's batteries and, while holding the APPS key, reinsert the battery. Keep pressing the APPS button until the bootloader screen appears so that it says
Press I to install code...(it shouldn't take more than a couple seconds for the bootloader to appear). Press "I", and then in TiLP drag the appropriate .xxu file to the calculator. For example, drag the .89u if you have a TI-89 or the .9xu if you have a TI-92+. It will take about a minute or two to transfer and install Punix. Once it is installed, it will automatically boot into Punix. Be aware that Punix does not have "Auto Power Down" (APD) yet, so you will have to power down the calculator manually with 2nd-ON.