If you actually dig into the history of this, you see that the GCC developers were actually quite positive (even about C++) and that merging parts or even all of LLVM (even parts that conflicted: maintainers from gcc stepped up to explicitly say "I worked hard on this piece, but I am mot attached to it: let's throw it away if LLVM's version is better") came up quite often for the following year (there was a lot of interest from the link-time optimization people, as well as gcj for the JIT features), but in the end (much later) this came down to most of the promises from Chris Lattner not panning out. (I was remarkably happy that the comments on Phoronix actually got this right, so if you read over the comments there you see a lot of discussion of this.)
> > The lack of FSF copyright assignment for LLVM is a problem. It may even be a bigger problem than what we think. Then again, it may not. I just don't know. What I do know is that this must absolutely be resolved before we even think of adding LLVM to any branch. Chris said he'd be adding LLVM to the apple branch soon. I hope the FSF assignment is worked out by then. I understand that even code in branches should be under FSF copyright assignment.
> This is a solvable problem, and has been pointed out to Chris repeatedly, by many people, at various venues, for over a year.
> He keeps hand waving, saying that it's possible.
> Great.
> I say, enough grandstanding: it's not enough to be possible, it needs to be actual. If it is indeed actually possible to release LLVM under the GPL, then he needs to pick a version and GPL it. Then we can get serious.
> Make it so.
> He seems to be operating under the mistaken idea that the GCC community can go ahead and make plans around LLVM being free as defined by the GNU project, without it actually being so.
> > The lack of FSF copyright assignment for LLVM is a problem. It may even be a bigger problem than what we think. Then again, it may not. I just don't know. What I do know is that this must absolutely be resolved before we even think of adding LLVM to any branch. Chris said he'd be adding LLVM to the apple branch soon. I hope the FSF assignment is worked out by then. I understand that even code in branches should be under FSF copyright assignment.
> This is a solvable problem, and has been pointed out to Chris repeatedly, by many people, at various venues, for over a year.
> http://gcc.gnu.org/ml/gcc/2004-10/msg01146.html
> He keeps hand waving, saying that it's possible.
> Great.
> I say, enough grandstanding: it's not enough to be possible, it needs to be actual. If it is indeed actually possible to release LLVM under the GPL, then he needs to pick a version and GPL it. Then we can get serious.
> Make it so.
> He seems to be operating under the mistaken idea that the GCC community can go ahead and make plans around LLVM being free as defined by the GNU project, without it actually being so.
-- http://gcc.gnu.org/ml/gcc/2005-11/msg01065.html