How Does Bootstrap CSS Make Money?

Does anyone know how Bootstrap CSS makes money? I’ve been researching into how Bootstrap CSS makes money and found that:

• Bootstrap is owned by Twitter
• Bootstrap is free to use and redistribute for everyone
• Redistributors of Bootstrap should attribute the CSS back to Twitter
• Twitter pay for the hosting of Bootstrap CSS on a CDN for you to use, freely

It’s not obvious how Twitter makes money from Bootstrap. Obviously the development of it would cost money, but the hosting of it would cost even more. Here are the benefits that I can see of Twitter providing this service:

• People contribute to the code, which Twitter can then use – so they get free programmers
• Twitter ensures that if others are using their CSS, then other websites will have a Twitter look and feel. This means that people will feel comfortable with the style of Twitter and continue using it
• Twitter may get a community of developers that they can get access to for employment purposes. These developers will already be familiar with the CSS aspect of their website

Whilst these factors don’t make money, Twitter will get some benefit from making Bootstrap CSS free. Cost verses benefit, I can’t see Twitter making a lot of money by sharing Bootstrap. I think they must just be doing it as an act of kindness or an interest project.