Is it okay to upload slides based on others papers? In some seminar classes, one student presents a paper selected from top conferences or journals with the help of slides. Usually, there is a lot of discussion about the strengths and weaknesses of the papers. The plots or figures are usually not prepared from scratch for the slides, but are copied from the paper by taking screenshots. But is it legal or even ethical to publish these slides online?
It is almost certainly a copyright violation in the US. It's probably also defensible via a fair use argument (in court!). I think that the odds of getting sued or DMCA takedown noticed are pretty low, but I still wouldn't encourage the practice of uploading the property of others to the Internet without their permission. That's a reasonably big ethics issue for me. The easiest thing to do might be to use a placeholder figure "See Figure 2 page 6", or similar, in the uploaded material. You might also try asking the publisher for reproduction permissions. They all have a process, and it ought to be free and easy for purposes of commentary.