We have two kinds of licenses. One for NxFilter v4, another one for NxFilter v3.
NxFilter v4 can be used for any purpose including commercial one without a written agreement from us. You can build your own product based on it and you can rebrand it, redistribute it freely. This business friendly license is being applied to NxFilter v4, NxCloud, NxClient, NxUpdate, NxMapper, NxLogon, NxRelay, etc.
However, NxFilter v3 is only for non-commercial use. You can not use NxFilter v3 for any kind of commercial purpose and you can not distribute it with any modification.