Is Loopback.io is priceable?

I need to start using the API framework for my next Node.js project. So, considered to use Loopback.io. But, when I go to their website I can see that it comes under StrongLoop Company (IBM) and it has pricing for more than 50,000 api calls. But, they mentioned it was an open source project.

What I want to know is, whether using loopback is priceable or using StrongLoop features on loopback is priceable? May be my question is lack of knowledge. But kindly guide me on this.