Why, if Microsoft can make buttloads more $$$ than Apple on software alone, would Apple be worried about losing a few Mac sales to have the chance of also making buttloads of $$$$ - which should outweigh the loss in their hardware sales?.?.?
Because they don't make a lot more money.
MS's profits in 2006 were $12.6 billion, and Apple profit's last quarter were $1.04 billion, which is $4.16 billion/year.
Basically MS is only making about 3 times more profit than Apple. Yet they have a 90%+ Share of the Office Suite and Operating system market, vs. Apple's 5% share.
Now you can see why Apple doesn't want to licence it's OS, it's not actually that profitable.