I do not understand DRM/silverlight properly. Does this means that I won't be able to see what code is running in my browser for eg. JS collecting data in the background or use things like adblocker, greasemonkey etc.
But it is a paradigm shift in the sense that it is the first time that a change is introduced in HTML that restricts the user from accessing the actual content that is being displayed.
Effectively, similar changes to the standard could be introduced to prevent users from tinkering with ads, or to prevent users from opting out of data collection.
In that sense, it opens the way to your browser being more like your phone.
Again, it's not _bad_ in itself, but it is a paradigm shift.
Yes, but it's not JS. It's a plug-in the EME spec calls "CDM", and it is allowed to be anything, including kernel modules and hardware.
Websites that sign contracts with CDM plug-in vendors can use these unrestricted plug-ins, but you aren't allowed to check what they're doing because of DMCA.