[xixi77]

It could change in the future, but there are a plenty of languages that got pretty mainstream while closed source -- in terms of working with numbers and data, I'd definitely call matlab and sas mainstream, stata and mathematica are nearly mainstream, R of course is open source which is a huge reason for its popularity, but it's a clone of closed-source s+ which was fairly popular already. In the general-purpose world, c# and swift got most of their traction while still closed source, etc. Surely there are more examples in other domains... But yes, there is definitely a very welcome trend to open source stuff.