Can any recommend an open-source Skype? [View all]

I only use Skype for text messages and occasional file up- and download.

Lately, it's been beginning to bug me with ads in the chat window and, additionally, I've serious security concerns with it being owned by NSA-friendly Microsoft now. I used to run an older version, but I just got signed off by Microsoft for not having the latest version.

I used to have nice open source chat programs like GAIM, which operated in a minimalist fashion and incorporated most known chat protocols but, as far as I'm aware, not Skype. Sadly, all my contacts have now moved to Skype and it's no longer an option.

I know that Skype used to be nearly impossible to reverse-engineer because of all the pains they had taking to prevent it. Is there a decent open source equivalent that will also run on Windows 8?

To clarify, I do need it to connect to Skype users so alternative protocols are not an option.

Thanks in advance.