U.S. patent No. 6,473,006, “a method and apparatus for zoomed display of characters entered from a telephone keypad,” has a long and tangled history.

It was originally filed, according to FOSS Patents‘ Florian Mueller, by a company called Phone-com, which assigned it to Openwave, which sold it to Purple Labs, which sold it to Myriad, which sold it to Google, which sold it to HTC last week for a price Google has declined to disclose.

On Wednesday, 6,473,006 turned up in a pair of lawsuits — one filed at the U.S. International Trade Commission in Washington, the other in a federal court in Delaware — filed by HTC against Apple (AAPL).

The iPhone, HTC claims, has violated this patent that came to HTC by way of Google, Myriad, Purple Labs, Openwave and Phone-com.

HTC, of course, is suing Apple because it was sued last year by Apple  — the first of many complaints Apple would  bring against the manufacturers of devices running Google’s (GOOG) Android operating system. Apple claimed at the time that HTC had violated 20 of its patents.

Tit for tat, right? Not quite.

The difference is that Apple actually invented the technology it accused HTC — and by proxy, Google — of “stealing” (to use Steve Jobs’ verb). One of the patents Apple cited in its 2010 suit — Patent No. No. 7479949 — is a 358-page document signed by Jobs himself that covers everything from the way a finger touches the screen of a smartphone to the heuristics that turn those touches into commands.

HTC and Google, by contrast, are accusing Apple (whose smartphone designs they have plainly copied) of violating patents they bought fourth or fifth hand.

“Patents were meant to encourage innovation,” Google’s chief legal counsel David Drummond wrote last month in his famous open letter “When patents attack Android.” Google’s enemies, he complained, were using “bogus” patents to try to “strangle” Android.

“Fortunately,” he added, “the law frowns on the accumulation of dubious patents for anti-competitive means.”

Indeed.