German writers used the phrase "gleichschwebende Temperatur" to denote equal-beating temperament since the beginning of the 18th century. This is not to be confused with equal-temperament, and instead actually denotes certain meantones, well-temperament, and other tunings where the varying temperings of different intervals results in them having equal numbers of beats per second.
However, most German writers have in fact used the term (and its variant spellings "gleich schwebende Temperatur" and "gleich-schwebende Temperatur") to designate regular 12edo, and unless the context specifically indicates that a well-temperament or meantone is under discussion, "gleichschwebende Temperatur" in German treatises generally refers to 12edo.
(Note also Schoenberg's frequent use, in his Harmonielehre, of the term schwebend to refer to a method of composition in which the sense of tonality is "suspended, floating", thus leading the way to his style of pantonality beginning around 1908.)
The tonalsoft.com website is almost entirely the work of one person: me, Joe Monzo. Please reward me for my knowledge and effort by choosing your preferred level of financial support. Thank you.