You keep using that word. I do not think it means what you think it means. From Wikipedia:
"""Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering."""
Nothing of this applies to Pepper API or NaCl. Mozilla can implement Pepper API and NaCl or can even just take NaCl as whole because it is, oh boy, oh boy, open source with a permissive license.
You think proprietary software is software that you can't use without license, but proprietary API is something other than an API that you can't use without license?
I mean the dictionary definition of "proprietary": controlled by a single proprietor, in this case Google. Google proposed the Pepper API on the plugin-futures mailing list a year or two ago, but Mozilla and Apple believed that it was unnecessary to maintain a parallel Pepper API for plugins to use when Web APIs were already there (and could be improved where they were not sufficient). Google implemented and pushed Pepper anyway. Thus, proprietary.
Likewise, Google is not open to input regarding the direction of NaCl, or whether it is a good idea for the Web. It is also proprietary.
Whether proprietary-but-open-source technologies are good for the Web is a separate discussion -- clearly, Mozilla and Google disagree. But it's unarguable that NaCl and Pepper are proprietary technologies.
You keep using that word. I do not think it means what you think it means. From Wikipedia:
"""Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering."""
Nothing of this applies to Pepper API or NaCl. Mozilla can implement Pepper API and NaCl or can even just take NaCl as whole because it is, oh boy, oh boy, open source with a permissive license.