and because Skype didn't own the IP for their p2p implementation, or even the source code to it.

"An executable-only object code form of the GI Software was licensed by Joltid to Skype, a well-known Internet-based company that provides users throughout the world with free or low-cost telephone services over the Internet. Skype did not obtain a license to the GI Software source code, however"[0]

[0] - https://techcrunch.com/2009/09/18/new-lawsuit-brings-clarity...