Forgive my stupidity, but...

Is this game still free? Since I played during the beta, will I ever have to pay? If I have a friend who wants to play, could he play for free? Or have to pay?

The game is free to play, although you can buy premium feature that gives you some privileges like creating world game, creating a coalition etc.

Citer:

How do Premium features work?
Afterwind is a free to play game - however, in case you want more, we have some excellent extra features that are available with Subscription or Feature packs. Subscription unlocks everything for a limited amount of time (1/3/6 months). Feature packs unlock specific sets of features forever. There's also a 'Full package', which is a full game buyout - it also includes access to any premium features that will be added in the future.

More information here http://afterwind.com/home/faq.php?faq_id=42

It's all about the Premium with these sites.

Actually, most of this game is available for free. Premium unlocks only a few things.

Also, the developers were kind enough to give a free premium account for life to all the beta players, which was thousands and thousands of people. If it was "all about the premium" they would have tried to make money instead.