User qbproger has contributed a distribution of Cobra with all Rhino-dependent code removed:
Users wishing to distribute Cobra as part of a propietary application can use the "nojs" version without worrying about complying with the GPL license of Rhino.
Rhino is released under a dual MPL/GPL license. While MPL libraries can be used in propietary applications, Cobra relies on a third party LGPL library, which is incompatible with the MPL according to the FSF. For anyone interested, there is a bug report open with the Mozilla Foundation that mentions this license compatibility issue: