I don't understand the sentiment of "once something is OSS, it has to be so forever". They owe you what exactly? More of their free time & money to hold up something you call a "promise" but is just their choice of license made many years ago?
They are being reasonable about it, you still get the source, you can still use it for free on a revenue < $25M. Companies making significant amounts of money now have to pay for it, instead of freeloading.
Its fine to spend your nights and weekends on passions projects when your young, its also fine to demand money for shouldering much of its development when said project grows large many years later and you have obligations towards your family. Its called being an adult.