Je ne sais pas si le-dit plugin est libre quelque part, mais la version distribuée sur les serveurs de MS ne l'est pas (suivre le lien indiqué dans l'article, lancer le .msi et lire):
Extrait:

2. SCOPE OF LICENSE. The software is licensed, not sold. This agreement only gives you some rights to use the software. Microsoft reserves all other rights. Unless applicable law gives you more rights despite this limitation, you may use the software only as expressly permitted in this agreement. In doing so, you must comply with any technical limitations in the software that only allow you to use it in certain ways. You may not
· work around any technical limitations in the software;
· reverse engineer, decompile or disassemble the software, except and only to the extent that applicable law expressly permits, despite this limitation;
· make more copies of the software than specified in this agreement or allowed by applicable law, despite this limitation;
· publish the software for others to copy;
· rent, lease or lend the software;
· transfer the software or this agreement to any third party; or
· use the software for commercial software hosting services.

Et sinon, à propos de l'attitude de MS face au libre, la façon dont ça colle parfaitement au célèbre aphorisme de Gandhi est caricaturale:

First they ignore you, then they ridicule you, then they fight you, then you win
- Mahatma Gandhi

(On en est vaguement au niveau de la 3ème virgule ;)