Yes! Blokada started as a hobby project, it's a way of giving back to the community. The app is open source, the advertisement filtering functionality is free, and it will stay this way forever. That said, developing it takes a lot of time, so please consider supporting the project in any way you can (see here).
Blokada Tunnel is an optional, premium feature that is paid. You can still use Blokada without ever enabling Blokada Tunnel. This way we can support the development while keeping the app itself free forever.