Have tried to download the free version but it says my system is only 10.7.5
First of all, go ahead and update to Yosemite, then try to download. Then it should be able to be used, Yosemite is 10.10 and not a cheapskate version. Apple now makes free updates that are quality. Now that I got that out of the way, just download Yosemite and it should work.
Hope I helped.
I know it’s old… but I have to say:
I run into this post all of the time. It’s bullshit. That does not answer the question AT ALL. He/She didn’t ask how to upgrade to Yosemite. The question was “What version of Unity runs on 10.7” not “How do I upgrade my computer”.
It’s something in the 4.x Unity3D cycle or earlier. According to this macOS 10.7 doesn’t support the Unity3D editor in the 5.x cycle https://forum.unity3d.com/threads/official-5-0-dropping-os-x-10-6-support-for-editor-players-dropping-os-x-10-7-for-editor.279182/