The licence allows other people to use source code for free but imposes certain conditions, including that any subsequent software made from that code must be available on the same GPL terms as the original code.
In 2004, a German court ordered a company to stop selling a wireless router because the company was not complying with the terms of the GPL. Last week the Software Freedom Law Center (SFLC) started the first US case to test the licence.
The SFLC has sued on behalf of the developers of BusyBox, an open source project, against Monsoon Multimedia. Monsoon makes time and place-shifting boxes for television recording and openly acknowledges using BusyBox in its machines, according to the lawsuit.
The case argues that Monsoon uses the software but does not make that software code available to its customers. The GPL says that anyone is free to use, copy and modify software issued under that licence, but on the condition that the source code is made available to users.
The SFLC argues that Monsoon has not made the code available, and is therefore in breach of the licence. Because it has broken the licence terms and continues to use the software without permission, it is infringing copyright, argues the case.
"Under the License, any party that redistributes BusyBox in a manner that does not comply with the terms of the License immediately and automatically loses all rights granted under it," says the suit. "As such, any rights Defendant may have had under the License to redistribute BusyBox were automatically terminated the instant that Defendant made non-compliant distribution of the Infringing Products or Firmware. Since that time, Defendant has had no right to distribute BusyBox, or a modified version of BusyBox, under any circumstances or conditions."
The SFLC is seeking an injunction preventing Monsoon from copying or distributing the BusyBox software. It is also looking for any profits made from the infringing sale of the products to be given to BusyBox, and to have its legal expenses reimbursed.
"We licensed BusyBox under the GPL to give users the freedom to access and modify its source code," said Erik Andersen, one of the developers of BusyBox. "If companies will not abide by the fair terms of our license, then we have no choice but to ask our attorneys to go to court to force them to do so."
"Free software licences such as the GPL exist to protect the freedom of computer users," said Eben Moglen, founder of the SFLC. "If we don't ensure that these licenses are respected, then they will not be able to achieve their goal. Our goal is simply to ensure that Monsoon Multimedia complies with the terms of the GPL."
GPL was originally written by free software advocate Richard Stallman and Version 2, the subject of the BusyBox lawsuit, is the same licence that underpins the widely-used Linux open source operating system.