In 2015, OwnCloud announced, “OwnCloud Server 8.1 Will Not Support Windows as Server Platform Natively.” You can find the OwnCloud’s rationale behind the decision to drop Windows Server support in their blog post. It seems to be a strategic decision from the OwnCloud team to focus on Linux and stop supporting OwnCloud Windows server.
ownCloud Alternative Windows – FileCloud
Contrary to the OwnCloud team’s experience, we find Windows Servers are very stable platform to host FileCloud. 60-70% of our customers run FileCloud on Windows Server. Also, FileCloud on Windows has excellent integration capabilities with Active Directory, NTFS file permissions, and existing Windows shares. We are expanding our partnership with Microsoft to bring FileCloud on Windows 2012 OS to the Microsoft Azure marketplace. Starting FileCloud version 14, FileCloud fully integrates with on-premise Microsoft Office Online server.
Detailed ownCloud vs FileCloud comparison