I don't think they're actually locked solely to HP printers by name, but in practice very well may be. However, they are using a standard. Here's the scoop (with a little background story).
Originally Posted by jhoff80
I decided to get rid of the USB printers around my house over the weekend (with part of the $450 I got back from Best Buy), and go all wireless printers. I bought two HP printers, a b&w laser printer, and a color ink jet. The Best Buy rep assured me both would work with the HP TouchPad (oops).
Got home, and both were recognized by the TP, but the laser printer would not print. I got a message on the device that it wasn't compatible (sorry, don't remember the exact wording), so I started doing a little research.
Turns out the TouchPad uses only PCL (Printer Command Language). This is a standard (though I think it is still owned by HP), but not all printers have it (including the wireless HP Laser printer I bought).
So, ensure that the printer you want to print to is:
BTW, my research also showed me that printing from tablets is not only something of an issue for TouchPads, but for virtually all tablets right now. For instnace, iPads only print to HP printers, and then only certain models.
Also, the notion that there is a some "standard" (besides PCL) is simply mistaken. Every printer manufacturer makes drivers for their printers to work wtih various computers. That's why when you buy a new computer, the first thing you have to do is install the proper drivers.
That said, there are some protocols that have been around long enough that they've become defacto standards, and some printer companies will default to those for some of the more basic printers.