Microsoft signed two deals this week with companies that agreed to pay royalties for technology used in Android devices, following a similar deal the software giant made with HTC last year.
The agreements could be indications that Microsoft has reasonably strong intellectual property claims on an operating system that Google has positioned as free and open.
On Wednesday, Velocity Micro signed a patent agreement with Microsoft for technology in its Android devices, including the Cruz tablet. The companies didn't disclose specifics of the deal but said that Microsoft will receive royalties from Velocity Micro.
Velocity Micro is a Richmond, Virginia, company specializing in building custom machines. It makes a Cruz tablet and a Cruz Reader, both based on Android.
Earlier this week, Microsoft announced a similar deal with General Dynamics Itronix, a company serving the defense industry. Its rugged computing devices include a small Android GPS device that users can wear on their wrists.
The deals follow one that Microsoft signed with HTC last year that similarly includes royalties for HTC's Android phones.
Microsoft has not disclosed what patents and technologies are part of the agreements.
At least one other company that makes Android phones has apparently chosen not to agree to a patent arrangement with Microsoft. Motorola is currently involved in a legal dispute with Microsoft over its use of Android.
Microsoft has licensing relationships with other Android users including Samsung and Sony Ericsson, but it's not clear if those deals cover the patents Microsoft is asserting against Android.
The fact that large companies like General Dynamics have agreed to pay Microsoft for technology used in Android indicates that the software giant must have a strong case, said patent expert Florian Mueller in a Wednesday blog post.
General Dynamics has the financial strength to defend itself in a possible lawsuit and is also patent-savvy, Mueller wrote. "So it's a safe assumption that General Dynamics had the knowledge that's required to analyze patent infringement assertions, and arrived at the conclusion that taking a license was the way to go," he wrote.
Microsoft isn't the only company chasing users of Android, which Google has positioned as an open-source operating system that can be used free of charge. Google is facing a legal challenge from Oracle, which is seeking royalties for the use of Android.
Apple has sued HTC over its Android phones and Motorola, perhaps seeking to head off a similar suit, has tried to invalidate the relevant Apple patents.
Nancy Gohring covers mobile phones and cloud computing for The IDG News Service. Follow Nancy on Twitter at @idgnancy. Nancy's e-mail address is Nancy_Gohring@idg.com