Is Skype available in Spanbox?

Yes. Skype has a web version, and Spanbox's whole model is that if an app has a web app, you can add it. So you sign into Skype inside Spanbox exactly like in a browser and it sits in your unified inbox with the rest, chats and calls. It counts as one of your apps (3 free, unlimited on Pro).

You can even run more than one Skype account at once, each in its own isolated session, so a work and a personal Skype sit side by side without logging in and out.