All: we took "open-source" out of the title. Let's stay on topic now.

I changed it on the blog too! :)

You could say "we're opening" or "we're opening up." Ambiguity removed, while keeping the original meaning.

Just a humble field worker battling the dreaded title fever, which drives souls mad like mosquitoes in the old North West.

It's a non-question. There's no defending them because they aren't being attacked in the first place.

Well at the very least, you'd expect "open source deck" to have the source file for the deck rather than processed image files. ;)

Yeah but "We're Creative Commons-ing our pitch deck" doesn't quite have the same ring to it.

While their intent is good, choosing the term "Open Sourcing" is not very genuine here. The pitch deck is nothing stellar (it's a run-of-the-mill pitch deck that we've seen before), and showing the slides only really lends ideas to others (ie. you can't literally treat them like an open source project and just modify certain parts, you have to rebuild the entire thing from scratch, and of course YMMV).

A more appropriate title would of been "Take a look at the pitch deck we used while vying for an $865M valuation".

"Disrupting vocabulary"