The first commentator and the only pre gaudiya commentator on Gopala Tapani Upanishad is Vishvesvara. I could find no information about him. His' is mix of monism and theistic commentary as Gopala Tapani has some advaitic type of content in it. The first gaudiya vaisnava commentary by Prabodhånanda Sarasvatî’s was influenced by the preceding commentary of Visvesvara.
Who is the first commentator Vishvesvara?