A minor quibble...
The author of the list has either not done all his homework or is not clear on the concept of open source. The freeware editor conText, on the list, is not open source.
From the conText FAQs:
Can I get ConTEXT source files?
This is a freeware project, not OpenSource.
However, I've used conText for years and agree that it's a very nice programmer's text editor.