Earlier quoted context omitted.
I saw the title and thought to myself, "No one has the right to tell open source volunteers how to spend their time! The only way an article with that title is acceptable is if it's talking about benefits to the DEVELOPER, not the user." Then I read the article and it IS using "should" in the sense of "I found this beneficial, you may too" rather than "this is an obligation".
For me (a non-native English speaker) the title was confusing for a related, but entirely different reason: it's referring to the kind of "office hours" a professor might have, not saying that you "should" work on your open source project during office hours (i.e. from Monday through Friday from 9 AM till 5 PM).
That was my first impression too.
Had to think that M-F 9-5 would not be enough for some projects, in total hours alone not just to accommodate different time zones.
Doesn't seem so bad to me, my "office" is staffed 24/7 and I always look forward to solving a user's million-dollar problem with a single phone call at any hour.
Even if it's not one of my regular clients. That's how some of the best ones got that way.