While the letterforms themselves are not copyrightable, as I understand it, the digital representation is copyrightable. This digitation of Neue Haas Grotesk would then be under copyright. Retracing Neue Haas Grotesk to create a free alternative would be a monumental undertaking, especially at such high quality. It took Christian Schwartz 6 years to digitize Neue Haas Grotesk.
Typography is a lot of work. Support the type designers and pay for their work.