museum-digital is an initiative aimed at allowing museums to easily and effectively manage and publish their (collection) data without compromising on data quality. Founded in 2009 by a group of smaller museums in Saxony-Anhalt with a strong focus on collaborative publication, museum-digital's scope has since expanded to offering solutions for much of the collection-related work of museums and working with over a thousand museums.
I personally have been helping out on museum-digital's software side regularly since about 2015 and have essentially taken over the role of a maintainer of most of the relevant software projects.
museum-digital's "frontend" is the software running the main publicly available portals of museum-digital, e.g. museum-digital:global. Using the software different museums' can publish their data (from collections to exhibitions to FAQs) on a common plattform.
More can be read on museum-digital's project website.