Only if you actually just browse baseball scores and play snake.
Think about what kind of open source contributions you could make in this job.
Probably nothing important due to copyright issues, company time + company resources means the company owns the work.
I do wonder if this is the origin of a lot of fun projects like "HN command line client" though.
It doesn't matter that you are not writing a thing.
If you're doing it on your private machine over which you have full control then how can anyone prove it was done during work hours?
I can sit bored (with a couple of hours worth tracking in the timesheet software) for a month or two, but then I usually start looking for something interesting.