“What does this say about Apple perpetual ownership of LQMT branding via MTA?”
Apple’s use of “liquid metal” isn’t covered under the MTA (but “liquid metal” is covered). So, to answer your question, it doesn’t say anything about the perpetual license.
Under the MTA, Apple can use the mark “liquidmetal,” if and only if, the product contains LQMT’s BMG. One could infer that Apple use of “liquid metal” because the iwatch doesn’t contain LQMT’s BMG.