I've paid for emulators in the past especially in the Amiga. I don't see a difference between an emulator and say IDEFix. They are both computer programs aimed at different users (or the same one if he/she is interested). Same goes for shareware games. A while ago, I had an argument in these forums about a game being shareware instead of being free. Why should a game be free, when the developer spends some time to get it going? Sometimes, such development efforts, have the developer devoting his free time in the project. Regardless of what kind of software this is, the author is given the right to release it as open source, freeware, shareware and so on. If winUAE was released as shareware, I would have paid for that simply because it's a lovely program that I use very often.
I would be more concerned to have all IDEs for free rather than having all software for free.