They're most likely MVP trousers - Moisture Vapour Permeable - which is a GoreTex equivalent. Bearing in mind that GoreTex is a trade name that has become synonymous with breathable water resistant material in the same way the Hoover is synonymous with vacuum cleaners then seeing GoreTex on something that doesn't also include "Genuine" and a proper label, I'd take it with a pinch of salt.