If we want to move to an education system whereby teachers are valued based on their ability to teach, and the performance of their students, then the teachers own their lesson plans. This is assuming, of course, that they developed the plan in the first place. Let's just say that's the case in order to make the discussion clearer.
Teachers, good ones, develop their methods for teaching students. If those methods lead to better student understanding, then let them sell them to other teachers. It's really no different than all of the stupid process patents that we rail over, except they're not actually trying to lock them away, they're trying to share them with their peer group and get themselves some benefit in the process.
I don't see a big deal here. They figured out how to build a better mousetrap, let them market it. Unless a school district contains similar "work product" provisions in their teacher contracts that many tech people have in theirs, the schools have no right to the processes and products developed by the teachers for their use.