(Update with lawsuit details) Apple today sued HTC for allegedly infringing on 20 patents relating to the iPhone. The simultaneous International Trade Commission and Delaware complaint accuses Taiwan-based HTC of copying elements relating to the iPhone's interface as well as its hardware and "underlying architecture." The American firm doesn't say what damages it seeks but claims HTC is thieving its technology rather than being original.

"We can sit by and watch competitors steal our patented inventions, or we can do something about it. We've decided to do something about it," Apple chief Steve Jobs said in a statement. "We think competition is healthy, but competitors should create their own original technology, not steal ours."

HTC is known to have been one of the more aggressive competitors to Apple in design, if not necessarily market share. It has developed a reputation of adding software features ahead of OS developers; it implemented multi-touch in the Android-based Hero even before Google had support. It accomplished a similar feat for Windows Mobile 6.5 with the HD2 and is best known for major interface layers such as TouchFLO on Windows Mobile devices and Sense UI on both Android and Windows Mobile. These have often centered on much more touchscreen-friendly interfaces and widgets.

Hardware design has only sometimes taken a cue from Apple, though this became more direct just last month with the unveiling of the Legend, whose unibody aluminum design with black inserts bears a more than passing resemblance to the original iPhone. It's not clear how much of the Legend or any of HTC's best-known software is affected by the lawsuit.

Update: HTC has officially responded to the lawsuit and says it hasn't been served the formal notice as of yet. However, it claims to be a "mobile technology innovator" that has patented many things of its own for the past 13 years. It declines to comment on whether or not any claims in Apple's lawsuit are valid.

An early discovery of the complaints ahead of their official posting online shows a number of broad-based patents at the heart of the suit, including gesture-based device unlocking, using heuristics in a touchscreen interface, and multiple power management techniques. Most of HTC's major smartphones from the past two years are cited as examples, including the Nexus One, the HD2, the Pure, all Touch Diamond and Touch Pro variants, and T-Mobile flagships like the G1 (Dream) and myTouch 3G.

The nature of the devices is superficially random and includes phones both with and without TouchFLO or Sense UI as well as Android and Windows Mobile, although Engadget notes that the Android phones were included specifically for their inclusion of Google's OS; it's not evident if the issue is Google's OS or simply the HTC features that Android enables. Windows Mobile devices are included primarily for hardware complaints.