Sender ID technology, which has been created by Microsoft to try and deal with the problems of spam, has been rejected by Apache. The Apache Software Foundation, who are behind the most widely used web server in the world, have rejected the technology on the grounds that it is incompatible with open source.
"We believe the current license is generally incompatible with open source, contrary to the practice of open Internet standards, and specifically incompatible with the Apache License 2.0. Therefore, we will not implement or deploy Sender ID under the current license terms."
Apparently, the majority of the Open Source community feels the same way.