In a Nutshell™ Clause Tax:
Tax means any kind of tax imposed by any taxing authority on any transaction or payment under this Agreement.
2010 GMSLA full text of Clause Tax:
Tax means any present or future tax, levy, impost, duty, charge, assessment or fee of any nature (including interest, penalties and additions thereto) imposed by any government or other taxing authority in respect of any transaction effected pursuant to or contemplated by, or any payment under or in respect of, this Agreement.
Eagle-eyed observers will not be able to help themselves remarking at the similarity between this definition and the one in the ISDA Master Agreement, which has that odd little cut-away relating to stamp duty.