the general bocu algorithm is covered by united states patent #6,737,994, which also mentions the specific bocu-1 implementation. ibm, which employed both of the inventors of bocu-1 at the time it was created, states in the unicode technical note that implementers of a "fully compliant version of bocu-1" must contact ibm to request a royalty-free license. bocu-1 is the only unicode compression scheme described on the unicode web site that is known to be encumbered with intellectual property restrictions.