Which of these two sentences is grammatically correct? 1- It is free and will always be 2- It is free and always will be
They're both correct. 2 would be more common I think. But it depends on the stress (on 'always' in 1. and 'will' in 2)
If you add another 'free', I'd use 1. "It is free, and it will always be free". They could both sound incomplete with another "it".