[eluser]Derek Allard[/eluser]
EE isn't released under an open-source license (hence, not really "open source"), however all the source code is fully available to you, fully editable by you, and not obfuscated in any way. A personal license for the forum is $50, which is pretty reasonable. If you consider how many days, weeks, and possibly months of work it will save you, I think you'll find its a good investment