LLVM is free software, and it is a confusion to equate copyleft and free software, though I still maintain that free and open source are very distinct concepts which refer to different categories of licenses. That contrast is better stated by RMS in the article on the subject above which I linked above.
Original reply:
Primarily its this first line here:
>LLVM is free software. You appear to be making the common mistake of confusing the permissive vs. copyleft distinction with the open source vs. free software distinction.
LLVM is NOT free software because it is released under the Apache license, which is an open source license but not a free software license. This is opposed to the linux kernel and GCC which are free software because their source is available under the GPL license. Further it is not really a confusion to equate permissive licensing with open source as distinguished from copyleft and free software. In this context, free is equivalent in meaning to copyleft, as distinguished from the more permissive open source licenses.