Is Vectornator really free?

Yes, Vectornator is completely free. However, it's unlikely to stay that way for long. I believe that their plan is to gather interest and a loyal user base as they develop the app. Then, once they have a finished product able to rival other industry-standard applications, they can start charging for it. Currently, their development of the app is backed by a team of investors, per their website. This allows them to continue development of the app without forcing the dev team to personally operate at a deficit. However, every investor will want to see some profit eventually; therefore they will start charging for the app.