Is it still possible to make webapps/programs (e.g. as Pidgin) to chat with Facebook friends using the new Facebook Platform (2.x) as chat.facebook.com is no longer available nor it is possible to get the full list of a user's friends.
Does this mean programs such as Pidgin won't work anymore with Facebook or am I missing the correct API calls?
Yes, those third party Apps will stop working after April 2015, when v1.0 will not work anymore, right now you can only use the Chat API in Apps created before end of April 2014. A new App can´t even use v1.0 (and the Chat API) anymore.