Because people would immediately call him a sell out. And because it then would be the property of whatever company, and he could be tied legally from recreating it.

I would imagine whoever bought it would write a clause to say he can’t create anything similar in future.

In those times there had been more than one popular free app that suddenly started installing crap on user’s machines.

I guess he just didn’t want to become attached to junkware being installed on people’s machines.

I don’t have the details but may they wanted to buy the source code from him and close it?