That's a larger problem I have with the Mac (and Windows, although less so) platform as a developer environment: all the cool tools are closed-source and paid. That's a serious barrier to innovation.
"Cool tools"? Needing ext#fs write support on OS X is a pretty niche application and I'm honestly surprised it's continued to be a viable business for Paragon all these years, especially with the rise of mainstream virtualization. I wasn't expecting to find them still selling it at all.
It probably wouldn't be there except I'm sure most of the expertise and code had to be developed for their imaging and partitioning products.
I think the only things I run frequently for development that don't come with OS X and aren't free or open source are Sublime Text and Paw. You can certainly use vim/emacs/TM2 and curl scripts if you want.
Were I using Linux, I'd be using Sublime Text, and, well, curl scripts again. I'd also be jumping off a cliff after about two days of dealing with desktop Linux's horrific regressions over the past decade.
OS X's native development tools (Xcode, llvm/clang) are free, and most of the tools you use in Linux are either already there, or a "brew install" away.
Edit: Seems it's still read-only. If you need write support that badly (why?), there's always Paragon: http://www.paragon-software.com/home/extfs-mac/