.. it's not possible to square libertarian principles with IP .. The debate is over. Principles libertarians know this.
.. The argument against IP does not rest on being anarchist or even anti-legislation. It simply rests on the assumption that property rights in scarce resources are a good thing. Once you accept this, IP becomes impossible to justify. You cannot have both: property rights in scarce resources and IP. RAther, you can have property rights in scarce resources, but not allocated according to Lockean-libertarian principles (first-appropriation and contract). You have to introduce a new ownership rule to implement any form of IP, one that takes property rights in already-owned scarce resources from the libertarian owner and transfers it to a third party, just like any other socialistic welfare redistribution scheme.
This issue is clear. There is a reason libertarians have flocked to it; once they turned their attention to it, the answer is obvious--to those who are honest and have libertarian principles. And it was seen, very very clearly, long ago: by Benjamin Tucker over a century ago, and then in revived form by Sam Konkin, and Wendy McElroy, and then (partially) by Rothbard, and then by Tom Palmer, and, then, starting in the internet age, 1995-, when the issue gained renewed importance, by the bulk of libertarians: Austrians, anarchists, left-libertarians. Even honest utilitarians should oppose IP ..
IP is utterly evil. It is completely in opposition to what libertarians stand for. Principled, honest, thoughtful libertarians pretty much all see this. Thank goodness. Too bad it is not yet enough to defeat this abomination.