VuFind is a library resource portal designed and developed for libraries by libraries. The goal of VuFind is to enable your users to search and browse through all of your librarys resources by replacing the traditional OPAC to include:

AquaBrowser is described as 'A "discovery layer" that provides a fresh, modern interface for patrons of varied backgrounds to use independently. By providing a simple interface with a single search box, patrons are able to quickly find relevant results when they need them' and is an app in the education & reference category. There are four alternatives to AquaBrowser for Linux, Mac, Windows, Web-based and Self-Hosted. The best AquaBrowser alternative is VuFind, which is both free and Open Source. Other great apps like AquaBrowser are Blacklight, Primo and Enterprise.
VuFind is a library resource portal designed and developed for libraries by libraries. The goal of VuFind is to enable your users to search and browse through all of your librarys resources by replacing the traditional OPAC to include:

Blacklight is a free and open source ruby-on-rails based discovery interface (a.k.a. “next-generation catalog”) especially optimized for heterogeneous collections. You can use it as a library catalog, as a front end for a digital repository, or as a single-search interface to...
Imagine a search that isn’t deterred by misspellings or human error. Where results populate in “rooms” based on content categories or themes. Imagine a search that not only spans the physical library contents, but newswires, databases and multimedia.