As noted here (see also here, here, here),

Texas Instruments has issued a DMCA notice to United TI, a group of enthusiasts. They had been cracking the keys that sign the operating system binaries in an attempt to gain access and possibly expand on the features.

Suing your own most dedicated fans of your increasingly outmoded device (its calculators), for trying to modify it to make it more useful to them. It's hard to decide what's more ridiculous: IP law, or the way companies use them. [SK cross-post; mises cross-post]

This was also reported on TechDirt, I responded there, that we need to debunk the myth that companies somehow retain "ownership" over the products that you buy. When you buy a product, a property right is conferred to you. The seller should not be allowed to assert that your use of a product, that you paid for, is at their sufferance.

Take the old car analogy. When you buy a car you acquire the right to modify it, to take the engine out and put a new one in. This holds true for electronic equipment. I reiterate, when you buy a product you acquire a property right to use that product.

By far the most ridiculous thing is to criticize what TI is doing without asking it why it is doing it. Several situations easily come to mind that if applicable make this a perfectly reasonable response.

No, they do not.

The only circumstance in which it is reasonable for the seller to maintain any say whatsoever in how their product is used is if it is still THEIR product; i.e. a rental or a loan. But if someone buys a calculator, that's pretty clearly a sale, not a loan. A loan would have a lower fee and a recurring fee or a return-by date. Not to mention the transaction would be structured as a loan. And the lender would be responsible for fixes, replacements, etc. not prompted by customer abuse. If the calculator gives up the ghost on you will TI replace it for free during your "loan"? Somehow I doubt it.