I'm of two, or maybe even three at some point, minds.
Owner of RM license hat from a profitability standpoint: I don't want a bunch of people creating material for my system with little to no control on quality when I could be making a percentage of that by them doing it through me and making sure the masses don't churn out a potentially large percentage of crap.
Owner of RM license from hat a 'legacy' standpoint: I'd love it if people started making a bunch of content for my game and, thereby, spread it's popularity with little to no effort on my end.
Personally, if I had the time to really dedicate to it, I'd rather just create the material and let ICE do the rest the work and pay me royalties. If I thought I could make a living at it I'd do it full time, but I don't believe I could with any system outside of D&D. Yes, I could go work for or maybe even start my own RPG company, but I wouldn't be making more than I do now.