I've seen suggestions from ex-Microsoft employees that the only reason they were even charging money for Visual C++ and the rest of their toolchain was to avoid

I've seen suggestions from ex-Microsoft employees that the only reason they were even charging money for Visual C++ and the rest of their toolchain was to avoid killing off the third-party market. They wanted to be as developer friendly as possible and that meant having a variety of choices so everyone could use what they liked most. Now that MinGW and LLVM have made it easy to get free and open source toolchains for Windows (and even MSVC compatible ones from LLVM) they do just give away most of their developer tools. They can't open source the compiler though because they don't write the C++ frontend parser/lexer, that comes from a third party.