It still either has to be a passion project for an engineer or it has to make business sense. Even if it only takes a collective week's worth of work in a year to keep it supported, that's 1/52 of an engineer's salary, and that has to be made up/exceeded by profit generated from the extra sales. Regarding this product, pens and drawing tables for personal computers are already a relatively niche category, so the subsection of those users who also use Linux is probably very small.