For me C89 means 'will build anywhere' whereas C99+ means 'may or may not build anywhere', rather than a value judgement about the author. But my background was in firmware where sometimes you were using custom compilers or very old compilers.
As someone whose idea of fun is trying to compile open source software on OS X / PowerPC, portability has a special place in my heart. While I view open source software as a "gift to the world", C89 + MIT is at the far end of the spectrum of how generous that gift is.