Microsoft-owned Skype has launched a campaign to shut down programmers who use reverse-engineering to understand its protocol and make interoperable products. Their PR agency calls this "nefarious attempts to subvert Skype's experience." Unfortunately for Skype and Microsoft, "experience" is not something the law protects -- after all, if a Skype user wants to talk to another person who uses a third-party Skype client, why would the law want to prevent that? Meanwhile, it appears that the sourcecode over which Microsoft is asserting copyright was created by the reverse-engineer they're harassing.
The day of publishing his initial details, Google's Blogger (where his blog is hosted) received a DMCA (Digital Millenium Copyright Act) notice that two of his blog entries had to be removed: the post about his success in reverse-engineering the Skype protocol and then a second post about more technical details.
The complainant issuing the DMCA notice was in fact "Skype Inc" and the basis for the complaint is "Source code. The publication of this code, in addition to infringing Skype's intellectual property rights, may encourage improper spamming activities." (Google publishes DMCA complaints to ChillingEffects.org.)
Skype issued a second DMCA copyright notice after this researcher published more Skype related code. Those files have since moved to being hosted elsewhere. Skype is claiming copyright on the code even though the open-source code was written by the researcher. Another DMCA takedown attempt regarding the same work was issued again in early August when the researcher tried doing a DMCA counter-notice, and he ended up putting up links again to this "copyrighted" work.