It may be open season on Android.

Google's mobile operating system has gone from promising new upstart in 2007 to a market leader in the United States, and with that, it's getting some unwanted attention. Legal attention.

That's one way to look at the patent lawsuit filed Thursday by Oracle, alleging that Google's operating system borrows from its Java technology, which Oracle acquired when it purchased Sun Microsystems this year.

According to the suit, Google built Android using Java applications and frameworks and though it utilizes a workaround meant to side-step Oracle's intellectual property, Oracle alleges that Google is still infringing on its patents.

The issue has raised eyebrows in the software community, particularly because Java is generally considered a free open-source technology.

While Android probably was an eventual target of Oracle, its recent ascendance has probably made it even more attractive to patent holders. Android recently eclipsed Apple's iOS and Research in Motion's BlackBerry operating systems to become the top smart phone platform in the United States.

"What always happens with phone technology is once they become popular, the lawsuits come out," said Allen Nogee, a wireless technology analyst at research firm In-Stat. "Android is growing nicely with more market share, and now it's time to jump on the platform to gain from that. That's how companies work."

With Google's backing, Android may not just be a lucrative target, but perhaps an easier target. While Google has built up a formidable array of patents in search, it may not have a deep portfolio of mobile patents to counter rivals looking to sue it, said Mark Driver, an analyst with Gartner. Oftentimes, companies settle patent disputes by agreeing to cross-license each other's patents.

"When vendors of this size fight, patents can act as a deterrent on both sides. The fact that Oracle has come out with a public lawsuit suggests that Google's patent portfolio around this particular vendor must be weak," Driver said. "And if they don't have a strong portfolio, that could be trouble in the future."

It could be trouble not just for Google but also partners who use Android. HTC, one of the leading smart phone manufacturers using Android, has also faced its share of legal challenges about its use of the operating system.

Apple sued HTC in March, alleging 20 patent infringements on issues that include the underlying operating system. That case is still being heard.

HTC also agreed in April to pay Microsoft an undisclosed sum and inked an intellectual property rights licensing deal to provide coverage for its Android phones. HTC declined to comment for this story.

Google, for its part, has vowed to fight the Oracle patent suit.

"We are disappointed Oracle has chosen to attack both Google and the open-source Java community with this baseless lawsuit," the company said in a statement. "The open-source Java community goes beyond any one corporation and works every day to make the web a better place. We will strongly defend open-source standards and will continue to work with the industry to develop the Android platform."

But the Oracle case probably will not be the last, said analyst Will Stofega, of IDC. He said the mobile sector in general is becoming rife with patent lawsuits as smart phones become an even more popular technology. And Google will get its fair share as it leads the smart phone market.

"Google created this thing, and it has deep roots in a lot of different things," Stofega said of Android. "If you get someone good enough they can find a potential patent conflict."

But most analysts don't believe the threat of patents will derail Android's success. If it can't prevail in court, Google may end up paying a licensing fee to Oracle, which it could swallow or pass on to its hardware manufacturing partners. It could mean charging vendors to use Android for the first time, though that wouldn't be a significant problem, said Ken Dulaney, an analyst with Gartner.

"If you're a manufacturer today and you look at your choices, Android is still the best option," he said. "This is the only really viable alternative to beat Apple, so it would be worth the cost."