First of all, the important part: It doesn't! :-)

Probably you are referring to the "Virtual Memory" figure in Activity Monitor.app. This figure includes much more memory than what the application has actually allocated. First and foremost it includes the full size of the process's address space, not how much of that space it's actually using. Since fruux also uses garbage collection (a new "low level feature" introduced in 10.5 Leopard). The garbage collector itself reserves several GBs of address space (but this space is not really in use).

So no problem at all. No bug with the garbage collector and no bug in fruux. It's just the "Virtual Memory" figure (on 10.5 Leopard systems) in Activity Monitor.app which is not really meaningful, especially with 64-bit applications.

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