More specifically, we're not porting Bootstrap to React but building React-specific components from scratch to fill the same gaps.
Something in particular we're focusing on is building a modular IU toolkit - so you could use all of Elemental, or just our select component / buttons / date picker / etc; all of which would be available as standalone packages on npm, but can leverage a consistent thumbing system and play nicely together.
(And yes - we'll fix that modal issue soon with a pure css approach; a community member wanted to implement it with JavaScript but it hasn't worked out well)