Download of OS33 1.0.1 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The software lies within Productivity Tools, more precisely Cloud Services. According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. This free Mac app is a product of OS33.
From the developer:
OS33 lets you securely access and view your files in cloud from anywhere. You can manage password and security options. Host any vendor application, custom solution, legacy software, ERP, etc. Browse your work folder and all the changes are automatically uploaded to the cloud.
You may want to check out more software for Mac, such as Everport - for moving 37signals' Backpack data to Evernote or Zeta Uploader, which might be similar to OS33.