That is one of the main reasons why there are so many open source projects; many developers are bored in their day jobs and want to scratch their interesting pr

That is one of the main reasons why there are so many open source projects; many developers are bored in their day jobs and want to scratch their interesting problem itch in their free time. But you have answered your own question: if you want to work on an interesting problem full time and get paid for it, one of the best ways is to start a SaaS on something you like.