There are full opensource alternative for this? I like the product, I'm testing it right now. But I'm curious if there is a way to accomplish something like this with existing opensource tools or a similar full opensource project.
There are other tools that exist anyway, but all the big ones (Fiddler & Charles, for Windows & OSX respectively) are very much closed source. The other similar open source competitor I'm familiar with is James Proxy (https://github.com/james-proxy/james) but that's now effectively unmaintained.
For comparison, using the internals of Fiddler by itself would cost $2,999 per application per year (https://www.telerik.com/purchase/fiddlercore). The standalone internals of HTTP Toolkit OTOH are on GitHub: https://github.com/httptoolkit/mockttp.
Though, as a development tool, I don't see any issues using AGPL software.
It's really just the runnable desktop app part that's AGPL. That encumbers you if you're making a directly derivative work (no running off with the whole app but closing the source, thank you), but otherwise it shouldn't limit you at all. This isn't like using a (A)GPL library in your codebase; it's a full application and you're an end user.
Morally bad and ultimately self-defeating, but I'm guessing legally fine?
In practice, I'm not too worried. It's a fair bit of a hassle, as you'd have to rebuild everything yourself. It'd also require a fork that would make keeping up to date with the main versions new features painful, and it's been moving pretty quickly!
It's only a few dollars a month, if that's expensive enough for you that the time & hassle to fork the whole thing would be worthwhile, email me at tim@httptoolkit.tech and I'll just give you a free subscription.
I think I more saw it as a challenge to be honest! But if I do get to that point in the future I may take up your generous offer.
Great README docs by the way - spot on in content and delivery!
You can, however, write small python scripts that have read-write access to the http flow (request and response objects).
I guess it's a more low level tool, because it doesn't provide mocking and other helpful tools out of the box.