Hello,
Windows is a pretty popular operating system, even though it sucks. In fact, a lot more people use Windows than they do Mac, or Linux and I feel that porting Orion to Windows will bring in far more users.
While I am switching to Linux in a few days, prioritizing Windows support will lead to a larger userbase faster, which I believe may allow to team to grow large enough to support the project if it were open sourced.
Also, they don't have to accept any pull requests if they don't want to.
Most web browsers like Arc browser, Chrome, Brave, and even Firefox are all cross platform. They support multiple platforms, including Mac, Linux and Windows, with Windows being where most of their userbase comes from.
By expanding Orion support to Windows, you will very likely attract far more users who have been wanting to try Orion out, but just didn't have a Mac to actually use it.
And while Linux users wait for native Linux support, they could probably use WINE or Proton to run the Windows version on Linux.