MS wants to own everything. If they suceed with the antispyware (aka defender, what a stoopid name), and with this antivirus, they could drive most of the anti virus companies out of business.
I dunno if they will start charging money for it, if they were smart, they'd just leave it as a free d/l if you validate your copy of XP (validation is not activation, all copies of XP have to validate to do most manual MS downloads nowadays). Might reduce the number of non legit copies ppl have if they knew they'd get a bunch of bonus software with a legit copy. I.e. add value to owning a copy.
What if they start selling Vista and adertising that it includes an option to get antivirus, anti spyware, etc with it? Norton/Mcafee, etc retail sales would crash lol.