Comment 1 for bug 1670268

I disagree. This is an elided version of "Some [of this software] is proprietary", which is perfectly grammatical. While "Some are proprietary" would be a grammatical sentence in isolation, it would be incorrect in this context, because "software" is not a count noun and so there is no plural referent available.

It may be worth rewording this entirely to avoid other people being confused in the same way, though.