It might be, but we're talking law, not logic. Copyright law has no obligation to logic.

> TPT is selling lesson plans and live teaching materials, not books. (Or at least they could reasonably make this argument)

They can call them moon modules, and it wouldn't matter. Copyright law has no concept of "book" or "lesson plan". Copyright protects the work. It doesn't matter if you're redistributing prints of a photo, or selling a JPG over the internet. Copying and redistributing a copyrighted work (in any form) is the violation.

> Also, the packages typically include references.

As do many books, but it doesn't exempt them from copyright obligations.

> Teachers using these materials should be aware that they are potentially infringing on copyright, thus could be sued.

This is where you have it backwards. The teachers who use the materials (probably) aren't breaking any laws by using the materials. They're covered by the teaching exemption. TPT, however, has copied and distributed the works in exchange for money. That is a pretty clear violation of copyright expectation.

> Like I said, TPT could be saved via DMCA, and the teachers are the ones that could be sued. The teachers would then be protected by the teaching exception. My point was that the lawsuit is not an obvious winner.

TPT, being in the position of a facilitator, might be safe, but there are two types of teachers in this equation. There are teachers using the lesson plans, and teachers selling the lesson plans. Those selling the lesson plans are at risk, IMO.

Simply being in the teaching profession doesn't automatically exempt you from copyright law. Laws are largely concerned with acts and context. Copying and distribution are both acts. If the context is that of teaching (as in the act of teaching, not the employment), then there is an exemption. Specifically, a teacher may copy and distribute (by incorporating it and showing it to students) a copyrighted work without penalty, provided the teacher is in the act of teaching.

I agree that the lawsuit is not a slam dunk -- very few lawsuits are -- but I don't think this for the same reasons as you.

I think the reverse is true here. An individual plan isn't that different from a compilation of plans. The rules of copyright still apply and the teaching exception does not apply as distribution (for sale no less, though there are free plans on TPT) is not exempted.

Including a reference to the source doesn't remove the liability of distributing/selling a copyrighted work which the distributor doesn't have a license for.

> Like I said, TPT could be saved via DMCA, and the teachers are the ones that could be sued. The teachers would then be protected by the teaching exception. My point was that the lawsuit is not an obvious winner.

I stated this elsewhere but the teaching exception doesn't cover copying or distributing a work to other teachers or for sale. It provides an exception for the purposes of teaching face to face or in the case of an online course, electronically to a registered student.