It’s free to forward incoming Skype calls to another Skype contact. You just need to have that contact in your contact list.
To forward your incoming calls to a mobile or landline, you’ll need a little Skype Credit or a calling subscription that covers the country you want to receive the forwarded calls in. If you use Skype Credit, forwarded calls are charged at Skype’s low per-minute rates.
The person who is calling you on Skype doesn’t pay anything.