Just noticed that the current LimeWire beta (4.11.0) includes optional copyright filtering. See the features history and brief descriptions for users and copyright owners:

In the Filtering System, copyright owners identify files that they don’t want shared and submit them for inclusion in a public list. LimeWire then consults this list and stops users from downloading the identified files “filtering” them from the sharing process.

If you sign up for an account as a copyright owner you can submit files (with file name, file size, SHA1 hash, creator, collection, description) for filtering. Users can turn the filter on and off via a preference.

LimeWire.org now features a blog with pretty random content. I notice that another PHP Base32 function (which makes a whole lot more sense than the one included in Bitcollider-PHP — I swear PHP’s bitwise operators weren’t giving correct results and worked around that, but was probably insane) is available with a hint that someone is building an “open source Gnutella Server in PHP5.”

Remember that LimeWire is Open Source P2P and thus pretty trustworthy — and you can always fork.