[freshyill]

Then the welcome.md is out of date. It's been open sourced.

[espadrine]

Something can be open-source and paid for. It is uncommon, because people can build it on their own, but Sublime Text is an obvious counter-argument: people are ready to pay for development, even when they could use it without paying.

[ben336]

ST isn't open sourced though, it just has a free trial that the developer has never chosen to put a limit on.