When was the last time anything from sp_ produced this kind of an improvement FOR FREE?
When I did opensource work i pushed the most profitable algos at the time like quark +50% faster. for FREE. I have done my opensource part for the community. Time to move on and let the cuda students take over. 4-5 years ago mining was done by the few in their garage and basements. Today you have bigger farms, bigger coins, and more money invested in equipment. Improving the money maker for free doesn't make sense anymore.
You'll earn a lot more from devfees compared to a flat subscriber's fee if you release your mods publicly, assuming that they are indeed the best for the given algo.
EWBF still earns $6000 PER DAY even though he abandoned his miner a year ago. Claymore earns more than $10k per day from his devfees.
Yes, there are always ways to disable the devfee, but they are a very very tiny minority that are not even a rounding error. Think about it.