Metaforce 3.1.6 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This free Mac app is a product of Metaforce. The application lies within Developer Tools, more precisely IDE. We recommend checking the downloaded files with any free antivirus.
From the developer:
Metaforce is a lightweight salesforce IDE. Based on front-end technologies (e.g., nodejs, bootstrap, etc.), it builds a modern and elegant UI to provide many features for salesforce development. With this app, you can manage salesforce organization credentials without a password. You can create, update, refresh, and test apex classes and visualforce pages easily. Salesforce metadata (XML file) can also be retrieved and edited in Metaforce.
You may want to check out more Mac applications, such as HexDecBin, wxFormBuilder or Ch, which might be related to Metaforce.