Upfront disclaimer: I use Linux on a daily basis
For a product like Construct2 doing a "linux" version is, in my opinion, not such a great idea.
There is no single linux os, it's a kernel with quite different environments depending on the distro. And a product like Construct2 attracts a lot of shall we say hobby- and home-user customers. They (Scirra) would have to deal with a lot of different distros and can't just publish an unpackaged linux build - people sometimes have a hard time building packages themselves, the shared library model of linux and open source drivers like nouveau with their caveats require some expertise, if you operate closed source software on such systems. That can't be compared to the software the distro maintainers build themselves and is relatively easy to handle for the distro users.
Imagine the support load, if you have to deal with 50000 kids who don't know how to preload libraries for example that must override those of their distro. That's not exactly the thing you want to deal with as a 2-man-company.
In a distant future they might as well switch to a browser based model for their IDE, that would make more sense.