Is it legal (assuming US) if instead of paying for a proprietary software and accepting their terms and conditions for distribution, to require the user to own this proprietary software and use it as a dependency for your software? e.g. Instead of accepting Unity's TOS and paying for Unity, to distribute to the user (commercially) a set of source code that require Unity in order to be built and run with a simple installer executable that automates the build process.
Furthermore is it legal to distribute alongside those sources a script that guides the user through the download of Unity, such as automatically downloading it, then opening a browser to accept TOS, without hiding away any legal conditions the user need to accept?
Extra clarifications: 1) I don't actually intend to do this, it was just a thought experiment on whether this was legal. 2) I would assume the game is distributed on PC and 3) the fact that the source code is now revealed to the user is irrelevant since this question is a thought experiment.