Machine code can be decompiled too, even if not as cleanly. It would slow down efforts to make an unauthorized fork of the software as a whole, but anyone curious enough about individual bits and pieces could still see exactly what's happening. Closed source is really more of a legal block than a technical one.
Given that and the lack of popular, high-level languages that compile to machine code (C++ is the best I can come up with), I'd reconsider whether that's really a priority.
True that any program can be reverse engineered. But for example with Python, you're not just handing them the program, but also the bytecode, which can be turned into source without spending much time. This gives a lot more information much faster.
I would prefer something like C++ which is about as obfuscated as you're going to get, but I'm curious if there are any higher level options that would save programming time.
Given that and the lack of popular, high-level languages that compile to machine code (C++ is the best I can come up with), I'd reconsider whether that's really a priority.