Apple offers a 90-day free trial of the current version of Logic Pro. To get an older trial version like 10.6.3, you would typically need to have downloaded that specific installer while it was the current version.
If you have previously purchased Logic Pro, you can download 10.6.3 on an older Mac. Open the App Store , go to your Purchased tab, and click the download icon. macOS will recognize your older system and offer to download the "last compatible version". logic pro 10.6.3 free download
There is no "free" version of Logic Pro 10.6.3 available for permanent use from official sources. You can, however, access it through these legitimate methods: Apple offers a 90-day free trial of the