OP's project is literally the reverse of taking a traditional desktop software, e.g. a graphic editor, and making it into a web app. Here, it's something that naturally belongs to a web site, but instead packed up into an installable desktop app.
I'd be really curious to see the rationale behind this.
I've been using some web-based tools. Somehow, they don't last (ie. namemesh, or domainsfortherestofus that @pwdisswordfish8 mention went offline for sometimes).
Then I thought having a desktop app would be great. For the long term, I don't have to worry the site is down.
You concern as stated does not apply.
It's much easier to install spyware via an actual desktop app than via a web app.