7-Zip's RAR (uncompress only) is licensed from WinRAR, so you still
have to download the proprietary RAR in these ways:
1. The 'unrar' for Linux
2. WinRAR
3. 7-Zip's RAR implementation is licensed from WinRAR, so they cannot
give out source to RAR. (p7zip, for example, does not have RAR support
at all)
4. Any other program with RAR licensed from WinRAR.
--
Mike