If you don't want to end up going to court with Autodesk, or any other kind of Autodesk. Then you'll need to cough up the AU$2000 or so just to be able to sell anything that uses assets made in 3DSMax for example.
That's option 1. Option 2 to infinite is to use Open source programs rather than proprietary ones. 3DSMax = Blender, SourceTree = Gitkraken (It's just better), etc.
The Major Project I'm part of for this and next trimester encountered this issue so it had to be resolved.
We're good with Unity since they're policy dictates that they do not take ownership rights of any content you make, you are the sole owner and holder of the copyright.
With that legal talk, Unity can take your data it collects with their client and use it to optimise and adjust their services. You can read more about it here.
Blender for example is Open Source under the GPL license. The GNU General Public License v3.0 says that you may use the licensed material for commercial use, distribute it, modify it, patent it and private use. But you must disclose the source code if somebody asks for it and any modification becomes licensed by GPL.
MIT is a better license overall since it allows for the same permissions as GPL except patents. And it doesn't license any modifications you make under itself.
Just a disclaimer here, I'm not a lawyer or working in the law field. So don't take my writing above as absolute, do the research yourself.