That's exactly right, Parchment is the web-based interpreter for Z-Machine games, like those created with Inform. Support for them was added 18 months ago.
Thank you, felixp.
Couple of questions regarding Inform. Is that the one where a room called The office would be created with The office is a room.
I've heard it said Inform is far more complex than most and is more suited to those familiar with programming. Is this the case?
Also, as every one of these games I see looks identical, does that mean Inform doesn't provide full customisation like Twine and Quest?
That would be Inform 7, yes. And you're right; it's one of the most complex authoring systems right now. But it's also a system that many non-programmers were able to get started with easily. I couldn't get used to it, but you should try it out, because everyone is different.
As for customization, I do believe Inform 7 allows for some amount of it when exporting to Glulx (the default nowadays), and even more when used together with the Vorple library. Most authors just focus on their prose, is all.