The suit is the first legal case in the US concerning the GPL, and could further validate the licence as parties including SCO and Microsoft have previously asserted that the licence is illegal and therefore non-binding.
The BusyBox tools offer Unix utilities for embedded systems, and the software is licensed under the GPLv2.
Although the GPLv2 allows developers to distribute the application free of charge, they are required to publish the source code for any changes that they make.
Monsoon Multimedia develops devices ranging from mobile appliances to Mpeg compressors. Although its products use a modified version of the BusyBox software, the lawsuit alleges that the firm refuses to publish the modified code.
BusyBox demands an injunction that blocks Monsoon from further distributing the software, as well as unspecified damages.
The BusyBox developers are represented by the Software Freedom Law Center which claims to have officially notified Monsoon about the licence violation earlier this month.
Colin Stiles, Monsoon's executive vice president in charge of sales of marketing, told vnunet.com that the firm had not received the legal complaint and could therefore not comment.
Even though the case marks the first time that GPL developers have asked the US courts to enforce the licence, it has been repeatedly upheld in Europe.
Harald Welte and Armijn Hemel, two developers from Germany and The Netherlands respectively, are heading up the GPL Violations project.
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