There are many alternatives to ownCloud for Windows if you are looking for a replacement. The best open source Windows alternative is Nextcloud. If that doesn't suit you, our users have ranked more than 100 alternatives to ownCloud and many of them are open source and available for Windows so hopefully you can find a suitable replacement. Other interesting open source Windows alternatives to ownCloud are Seafile (Freemium, Open Source), IPFS (Free, Open Source), Cozy (Freemium, Open Source) and Pydio (Freemium, Open Source).
Encode Explorer is an easy-to-use php script to use as an index file. It shows files in the server and lets you browse through folders, upload files etc. It is kept small and neat so that the source can be used for learning.