In the description of bfxr it's said that it's based on sfxr, but it's a bit improved etc.
They don't hide that. And yes it's a really good tool. Actually, I tried to (and failed to) create a protocol like for midi, but using values of bfxr instead. If you already used sfxr, you probably noticed that it's values (ranging from 0 to 1, "min" to "max"). So, the description of a sound is pretty small (smaller than would be any mp3 file for example :D). A small sound unit, yet pretty rich and versatile.
What I wanted to do was a sound synthesizer that would perform the same task as bfxr (or sfxr). So somebody doing a game, for example, you just send a small sound unit (the values) to the synth and obtain the result.
And so every game (in c, c++, java, c#, go whatever) could have such sounds (because it's a protocol, there is nothing to link, it's a third party program).
I always found very weird to use mp3 (or other complexe audio format) for such sound effects.