A few weeks ago the IPKat put out a plea for information concerning "non-asserts". He wrote:
"It sometimes happens, usually when an intellectual property dispute is settled by agreement, that the IP rights owner undertakes not to assert his right against the other party to the agreement. In theory the rights owner merely forbears to sue, but in practice it can be said to be a licence. Does any reader of this blog know of any reported cases -- in any jurisdiction -- which turned on whether the non-assert was characterised as a licence or not?".