Microsoft promised that it would offer its own DVD player app for Windows 10 a few months ago, and now that app has been launched. The catch is that it is currently available just for people who are upgrading their Windows 7 or Windows 8.1 PC with Windows Media Center.
Microsoft's web page says:
"The Windows DVD Player app is available free for a limited time for people running Windows 7 Home Premium, Professional, Ultimate, Windows 8, or Windows 8.1 with Windows Media Center. Please note that Windows Media Center isn't included in Windows 10 and will be removed when you upgrade to Windows 10. After the upgrade completes, Windows DVD Player will download automatically to your PC."
"To be eligible for the free DVD Player app, you must upgrade your Windows 7, Windows 8, or Windows 8.1 PC rather than perform a clean installation. If you're running an edition of Windows 7 or Windows 8 that doesn't include Media Center and you upgrade to Windows 10, go to Windows Store to buy Windows DVD Player or another app that plays DVDs. Provided your PC has an optical disc drive, Windows DVD Player will play DVD movies (but not Blu‑ray Discs)."
There's also a more detailed FAQ page in Microsoft's community forums about the Windows DVD Player app. It also mentions that the app will be available for purchase in the Windows Store for non-Windows Media Center owners but at the moment, that link is not available, nor is there a price mentioned for the app.