Aren't there two seperate discussions? 1. Paying something for the contribution of others that offer their product for free (OSS) and 2. Paying for and using proprietary software according to the licenses as offered by the licensee. Mathematica falls under 2 and is obviously totally allowed to pursue any pricing scheme they find acceptable. We just happen to think that leads to a lower than optimal rate of acceptance, which is a societal loss but Wolframs good right. Given Wolframs love of I and there being two I's in prIcIng, he must have written about his motivations somewhere.