Google have made the suite of Lightroom and Photoshop plugins, the Nik Collection, freely available for download as of today. There’s no strings attached, you don’t even need to sign up for an account, simply click the download button!
Some folks have taken this as a sign that Google are going to stop working on the Nik Collection, but this isn’t actually the first time Google have made the plugin suite free, and I seem to remember the same cries last time.
It’s not entirely clear how long these will be available, so if I were you I’d go grab them now even if you sit on it for a bit. It’s worth the trouble just to get Silver Effex Pro, but you’ll get a stack of other plugins as well.