Greed got in the way of good manners, when the original developer for The .NET port of the Lucene indexer pulled the original sourceforge project, and started marketing his open source software as a closed source commercial product!
It's one thing if he had actually come up with an independent idea and just regretted his open source licence, but he's just ripping off the (free) work of others. What an asshole. He even had the poor taste of leaving advertising for his commercial rip off at the original sourceforge project page (Google Lucene.Net - I'm not going to add Google juice). Thankfully this didn't go down quietly - the open source project is back as another sourceforge project in less greedy hands.