Who would risk using a closed-source language? I know some academic groups using Matlab, and I know some engineering companies use tools like Simulink, but these are very established products. I don't think I could even get sign-off for using a new closed language for a work project...
Sure if something similar happened to an open-source project, you would still have to either hire engineers to work on the compiler/tooling/language or to rewrite it in a more supported language, but I would consider it a little less riskier as you aren't dependent on one vendor