Which ACM copyright license to use? ACM now offers authors of published papers a choice of two copyright licenses: the "traditional" ACM Copyright Transfer Agreement or the ACM Publishing License.

How should I choose between these two licenses?  What are the advantages and disadvantages to the authors of each license?

I care a lot about maximizing the ability of others to read the paper (e.g., maximizing my ability to make my paper available on my web page, institutional repository, etc.); are there any relevant differences between the two licenses that affects this consideration?  Are there any other important differences between the licenses that authors might care about?
First off, please note that IANAL.

That said, the Copyright Transfer Agreement is what ACM used to be doing to everyone: when you publish with the ACM, you transfer your copyright to them, and thus lose ownership of your creative work. The ACM has been receiving criticism for this as the Open Access movement has gained momentum.

The Publishing License seems to be their response to this criticism: with the Publishing license, you retain copyright yourself, and instead grant ACM a specified list of rights:


An exclusive, worldwide, royalty-free, perpetual, irrevocable, transferable and sublicenseable license to publish, reproduce and distribute the work in any way they feel like — including to hand these right on to other parties.
A non-exclusive permission to publish, reproduce and distribute any software, artistic images and auxiliary materials.
These rights “infects” any minor revisions (derivative work with less than 25% new substantive material).


I don't actually know what the exact implications here will be — the conditions are restrictive, but the copyright remains with the author.