Before Mono there was no managed-code environment available under an open source license. Sun continues to stall and dance around the issue of open sourcing Java, but Mono is here now, and it works. According to de Icaza, it is no more vulnerable to patent lawsuits than any other open source application. Tellingly, Ubuntu Linux doesn't ship software to decode MP3 audio files because of intellectual-property concerns, but it does ship Mono. Have Mono's critics really assessed the risks fairly, or do they just hate the CLR because of where it came from?
Microsoft still has Visual Basic, but it supports IronPython anyway. In so doing, it has reasserted and demonstrated its willingness to support languages running on the CLR that weren't invented in Redmond -- even ones that were born as open source. Call it an olive branch or call it a publicity stunt; either way, surely there's room for a little transfer of technology in the other direction?