JGroups - A Toolkit for Reliable Multicast Communication

JGroups is open source licensed under the Library (or Lesser) GNU Public License (LGPL). Here are the main features of the LGPL with respect to its use by commercial products:

• A commercial product can use JGroups (as a library) without having to become open source under the LGPL. (This is the big difference to the GPL, where applications using it must be licensed under the GPL as well.) So, if you for example use JGroups to write a product for clustering an application server, you can sell this product without any restrictions (ship it with JGroups included) and you do not have to make your application open source.
• If an application makes modifications to JGroups itself, the modifications (not the application !) have to be sourced back into JGroups. Typically, how this works is that you will contact the JGroups project with the modifications for JGroups, and we then decide whether to incorporate them into JGroups, or not.