I would love to know whether it’s a settled matter that a FOSS reader app that ignores simple PDF restrictions would truly be considered illegal in the US. However, that’s probably a question best suited to a forum about legal issues.
In any case they’re useless restrictions that can be dealt with by anyone determined to do so, and the fact that Sumatra’s code even includes a DISABLE_DOCUMENT_RESTRICTIONS flag just waiting to be turned on makes the situation even more ridiculous.
Well, there’s no point debating about it. kjk’s decision is what it is and the official release isn’t likely to change in this regard, so all such requests are basically pointless. Folks can either go compile their own copies or use someone else’s pre-compiled version with the flag turned on. End of story.
Edit: I’ll just leave this interesting titbit here that’s straight from the horse’s mouth (i.e. the official PDF Reference from Adobe):
It is up to the implementors of PDF consumer applications to respect the intent of the document creator by restricting user access to an encrypted PDF file according to the permissions contained in the file.