After contemplating and doing some research we have decided to stay with #Bootstrap for Anahita 4.*
A simple comparison of the repositories on GitHub shows that Bootstrap has 7 times more forks and nearly 4 times more stargazers. I did a quick survey in #LaunchAcademy and couldn't find a single person who had used Foundation in the past, but there were a few who were familiar with the project.
Personally I am far more impressed by the #ZURBFoundation. If were building a SAAS or HTML5 mobile app, foundation is the way to go. However for an open source project, it is about accessibility and familiarity. When people start experimenting with Anahita, the first thing they do is trying to customize the user experience. In this case Bootstrap has an upper hand, because there are more options available for it.
In the mean time we won't be baking Bootstrap into Anahita the way it is right now. It should be possible to create a template using #Foundation and layout overwrites. If we ever built one for one of our client projects, we'll make sure to release an open source version of it on Github as well.
Let's proceed with the #MobileFirst implementation.