Copyright and patents are very different beasts.

For example there a lot of ways to use the so-called priority of the US patent to file other patents, including elsewhere in the world.

US Americans sadly often forget that the majority of the planet is not the USA. Here in Thailand, US and EU pharma companies have managed to get patents on 15 year old basic stuff like anti-histaminic meds. "Oh, but the system of limited monopoly in the US worked for us?". Yeah. But in Europe, the cost per pill is somewhere around $0.08. In Europe it's about $0.02. In Thailand it's $0.80 because Zyrtec managed to file a patent here re-using the priority of the US patent. And wage-adjusted in Thailand the cost per pill is about $15 per pill. You better don't have an allergy over here. So: Patents can have long-term consequences.

Back to IT: Have a look at the whole patent troll industry. The biggest chunk of junk patents that they bought are coming from "we will not do any harm" owners/filers. A lot can happen in 20 years.