LGPL is widely adopted license - you really have to learn what it is about as it is used in numerous projects.
This is the whole point in OCCT using a standard license instead of project-specific license - to easily identify project applicability.
A lot of proprietary applications depend on LGPL libraries without problems, as long as they follow several rules - see related section in the FAQ.
If your company has strict allergy to copyleft licenses, Open Cascade may also provide OCCT under other conditions to their commerical customers (hense, "dual license" in OCCT description).