I believe it stands for Free/Libre Open Source Software. I think the idea is to explicitly indicate both free as in beer and free as in speech. However, to me it just sounds like throwing in a romance term for the sake of it. But maybe I’m just ill versed on the whole free/libre divide?
How is #6 not specific to IDEs? I’ve never had vim, np++, or any other dedicated editor freeze; and I’ve used them to edit multi-gigabyte log files before.