What is proprietary from just their keys?
They are all Cherry MX compatible keys, its just that Corsair went with nonstandard spacing.
Also Corsair been really good about providing spare parts to their customers.
Their website sells spare parts, and in the past they also gave away spare parts to customers that asked.
Such as their customers who brought their CPU cooling kits, and was missing the AMD compatible parts opening up a RMA request got you the missing parts for free.