(No offense, but I just get very skeptical of “security” products that are ‘free’.)
The answer is in the third sentence of the parent comment:
Currently the VPN is applied to the browser only, so we're thinking of charging to switch the VPN on for device-wide protection.
Most browsers are ad-based and their business model is your data. They may add new privacy tools, but they have an identity crisis and can never go all in on protecting your data. We are not ad-based at all, so we can provide uncompromising support to protecting your data instead and that will be our business model. To pay our bills, we are considering offering premium support for people who want to expand our VPN service to all other apps on their device. We will look into partnerships to sell other privacy tools and browser extensions. In fact, we already have interest from other startups to customize our browser to work behind their own firewall, so we can offer custom browser support as well. So there are a variety of viable options that we're excited about and selling your data will never be one of them.