"Microsoft has warned open source developers off using its ASF
streaming media format. The author of VirtualDub, an open source
video capture and editing package which reverse engineered the ASF
format, has dropped ASF support after a call from Microsoft's
Windows Media group."
"Avery Lee, the author of Virtual Dub, says he received "a
polite phone call from a fellow at Microsoft who works in the
Windows Media group. He informed me that Microsoft has intellectual
property rights on the ASF format and told me that, although I had
reverse engineered it, the implementation was still illegal since
it infringed on Microsoft patents."
"ASF is indeed currently the intellectual property of
Microsoft, one of a clutch of posthumous - and highly contested -
patents the company has been filing since the new year."