In a perfect world, every copy of Internet Explorer below version
10 11 would be living out its days in a pleasant retirement home, playing bingo and fighting over the remote control with Lotus Notes, and the IE dev team would adopt a modern release cycle so that newer versions weren't constantly playing catch-up with the browsers built on open source.
Sadly that's not the case, and it's not just IE that's the problem - there are plenty of IT departments out there who think it's perfectly fine to lock their users to a version of Firefox that should have collected its bus pass a long time ago.
Fortunately, Ractive still caters for these browsers, but you need to use a legacy build. The legacy builds, which have obvious names like
ractive-legacy.js, include various shims and polyfills that allow the grumpy old browsers to play with the kids - things like
addEventListener, and so on. Newer browsers will simply ignore them, so you can use the legacy builds without any penalty other than the slightly larger file size.