Is Google fonts a good choice to choose fonts for our company Brand Book? What are the other affordable sources if not free?

We are rebranding our business and our design team suggests to go for a standard typography style. So we are looking for best and affordable fonts and stumbled across Google Fonts. Those are very good options and we need to choose Open sans & Rubik for our Brand guidelines book. Is this a good choice? It says open source license, what does it mean?

Using Google Fonts for print work

My experience with building websites is limited, but i have used Google Fonts (GF) for some basic presentation websites before. I was recently given some branding guidelines built by other providers which used GF for everything, including print items, eg. business cards, brochures, etc. And I did just use this identity to build a white paper for this client using GF, which seems to look ok even when printed on paper.