Whilst I enjoy Basic4android tremendously I would love to be able to create Linux apps in the same way as B4A allows Android app development.
Linux seems to be becoming more popular, largely thanks to solid releases like Ubuntu and Linux Mint, but also because of the negative reaction to the (dismal) Windows 8 re-design.
What's lacking for me though is an 'easy' way to develop apps. QT Creator is about as good as it gets. Basic4Linux would be super!
All it takes is a couple of extra parameters for UNIX-like filesystem navigation (no drive letters, use more logical and variable-driven paths, etc), and my single binary runs perfectly across both Windows and GNU/Linux.
Mono supports up to .NET 2.0 perfectly with near-perfect WinForms support.