This was kind of the birth of, in some ways, of open source software movement, which... which has gotten very popular recently. But it's different from the... from the so-called GNU Public License that... that is very successful today for... for most of the open source thing. It's different in one way, that the - one way that's very important to me - and that is that this open source GNU Public License software is... it comes with the saying that anybody can change it, not only can anybody use it, but... and they can modify it to their heart's content. I... I don't allow people to change TeX, unless they call it something else. So, if you... if you make... if you give it any other name whatsoever, then you're free to change it, but if you call it TeX, then it's got to be exactly the same as everybody else's TeX and... and the one that I personally have... have given... I...I have special programs that... that are used to validate whether... whether or not you've got... you've implemented TeX correctly. And so, that's different from the open source. In fact, somebody once looked at one of my fonts and said, oh I can improve that, I'll change the spacing a little bit, and as a result one of my books, all of a sudden, didn't typeset the same, and... and... they... but the... one of the early distributions of Linux included his so-called improved font, and... and I... but all of a sudden found out from my co-author that... that, you know, that he... that he was getting different... different paragraph behavior, and... and we traced it down to somebody, you know, making what looked to him, like an... like an improvement. That's what happens when you have complete, you know, when anybody can... can modify it and they - like the Wikipedia nowadays... you know, it's, you can go to Wikipedia and you can look at any article, and there's a little button you can press saying edit, and you can change anywhere in that article and it's... it's there, it's in Wikipedia. They don't even ask you who you are, making the change. I... I think that Wikipedia's enormously successful, but it's so brittle, you know, if I was... if I... if I spent a lot of time writing an article for the Wikipedia, and I wanted to make sure nobody screwed it up, I would have to check that article every day to make sure that it was still okay, and you know, but... after I've done that I want to move on and go on to other... other things in my life. With TeX, I wanted stability especially urgently because the... because people are depending on it to be a fixed point that they can build on. So in that respect, I... I differ from the GNU Public License.
