javascript - DingTalk's excel and word file previews are directly using Microsoft's office web app. Isn't it illegal?

Question

Microsoft’s office web app should not be open source.

Answer 1

No, if you search on foreign websites, only Microsoft has a set of open source protocols specifically used for this kind of preview. WOPI, you can learn about this, but to use this protocol, the server must be a windows server. There is also a set under Linux, but I have forgotten the details.