Red5 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 Red5 (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 Red5 to write a product for streaming and or data transfer, you can sell this product without any restrictions (ship it with Red5 included) and you do not have to make your application open source. If an application makes modifications to Red5 itself, the modifications (not the application !) have to be sourced back into Red5. Typically, how this works is that you will contact the Red5 project with the modifications for Red5, and we then decide whether to incorporate them into Red5, or not.

I give credit to JGroups for helping me explain the license ( http://www.jgroups.org/javagroupsnew/docs/license.html)