Mac users running OS X 10.5.8 and earlier can't use Skype anymore now that Microsoft has dropped support for the older versions of the Mac operating system. The change happened this week, leaving Leopard users without any way to use the voice and video chat app.
Want to run Skype on OS X Leopard? Sorry
The first indication many Leopard users had that they were being left behind came when they found out Skype's service simply stopped working for them. Microsoft's Skype team later offered up some details, saying Skype now requires at least OS X 10.6.
Here's what they said on the Skype forums:
there seems to be a lot of confusion around this. First, let me assure you that no-one is locking you out from using Skype on OS X 10.6 - 10.8 and there is no need to upgrade to Mavericks or (the new OS X now in dev preview) Yosemite if you don't want to.
All OS X 10.6 - 10.8 users can head over to http://www.skype.com/en/download-skype/skype-for-mac/downloading/ and get version 6.15. This is a very solid release and you can still use all of the main features without any problems (i.e. group video, group chats, screen sharing etc).
Note that you should only use the link above, it serves you with a correct update for your OS version, direct links (to DMG files) can work, but are not guaranteed to do so.
That said, we still encourage you to stay up to date, meaning upgrading to Mavericks and getting the latest Skype.
Hope this clarifies things a bit.
If you have problems updating, please let us know in this thread and I'll try to help you.
Microsoft stated earlier this year that it would stop supporting Skype 6.14 and older, but didn't offer a specific timeframe. That support included being able to login to Skype, which is what Leopard users encountered this week.
Microsoft is continuing to support Skype on the Mac, but will require users to run at least OS X 10.6.