The best open source alternative to FileRun is Nextcloud. If that doesn't suit you, our users have ranked more than 50 alternatives to FileRun and ten of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to FileRun are ownCloud (Freemium, Open Source), Seafile (Freemium, Open Source), Pydio (Freemium, Open Source) and Filestash (Freemium, Open Source).
You should have full control over your data. We help you achieve that: a safe home for all your data. Secure, under your control and developed in an open, transparent and trustworthy way. We are Nextcloud.
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.