Talk about dissonance. On the day Microsoft crowed that it was letting its employees contribute code to an open-source project, Joomla, it fired another shot at Linux.

On Wednesday, Microsoft announced a patent agreement with phone maker HTC that provides "broad coverage" under Microsoft's patent portfolio for HTC devices running Google's Android.

Ironically, Microsoft stands to actually make a profit from Linux. HTC will pay Microsoft royalties for each phone it ships with Google's renegade operating system.

HTC is just the latest notch on Microsoft's belt. Amazon, Novell, Linspire, TurboLinux, and Xandros have all signed deals with Microsoft to protect themselves and their users against litigation over possible violations of Microsoft's patents by Linux. As with HTC, no patents were named.

Satellite navigation maker TomTom, which uses Linux in its devices, was taken to court by Microsoft in March 2009 over violations of eight patents in its implementation of the Linux kernel. The companies settled, with TomTom promising to remove the offending functionality within two years along with some other, undisclosed, financial terms.

And now HTC. Mobile is a rich target. You can see a list of companies working with Linux here. Nokia, Palm, Samsung and Panasonic are all there, as is HTC. Consumer electronics manufacturers - some of whom are on that mobile device list - represent another big target. They've sucked in Linux for use on cameras, music players, DVD players, TVs, Blu-ray devices, and set-top-boxes.

Since 2007 Microsoft has claimed more than 235 of its patents are violated by Linux, but the company's never come out and said what those patents are. Instead, Microsoft's strategy is to pick off company after company that's implementing Linux. The approach benefits Microsoft, because it plays to the overall goal of monetizing its portfolio of patents.

Naturally, Microsoft's corporate vice president and deputy general counsel of intellectual property and licensing, Horacio Gutierrez, issued a statement pointing to the amicable nature of its agreement with HTC. Today's agreement is an example of how industry leaders can reach commercial arrangements that address intellectual property," Gutierrez said.

But an open declaration would mean that potential violations could be removed or that the claims could be exposed or potentially disproved. The failure to disclose the patents might benefit Microsoft in one sense, but the constant drip, drip of signing patent covenants will only serve to rile open sourcers and constantly eclipse any attempts by Microsoft to work with the community.

Articulating that mood, Linux Foundation executive director Jim Zemlin told The Reg: "Microsoft is once again demonstrating that it will attempt to use patents to muddy the waters about the viability of any competitive platform in order to maintain its Windows franchise."

Zemlin has been noticeably business-like with Microsoft in recent years. He's hosted Microsoft executives at the company's annual Linux Foundation Summit in San Francisco and stood up for the company when it was pilloried for donating thousands of lines of Linux driver code to the community because it had violated the GPL.

Reacting to the HTC lock down, Zemlin told us: "Developers will see this news for what it is and choose to innovate on open platforms as opposed to developing on locked-down operating systems from patent-wielding dinosaurs." ®