update virtualmin description, add license, language, source code link

- ref. https://github.com/awesome-foss/awesome-sysadmin/issues/416

README.md

@@ -287,7 +287,7 @@ _See also: [IT Asset Management]([Ralph](#it-asset-management))_
   - [ISPConfig](http://www.ispconfig.org) - Manage Linux servers directly through your browser. ([Source Code](https://git.ispconfig.org/ispconfig/ispconfig3)) `BSD-3-Clause` `PHP`
   - [Sentora](http://sentora.org/) - Open-Source Web hosting control panel for Linux, BSD (fork of ZPanel). ([Source Code](https://github.com/sentora/sentora-core)) `GPL-3.0` `PHP`
   - [VestaCP](http://vestacp.com/) - Open-Source hosting control panel. ([Source Code](https://github.com/serghey-rodin/vesta)) `GPL-3.0` `PHP/Shell/Other`
-  - [Virtualmin](http://www.virtualmin.com/) - Hosting panel for Linux based on webmin.
+  - [Virtualmin](http://www.virtualmin.com/) - Powerful and flexible web hosting control panel for Linux and BSD systems. ([Source Code](https://github.com/virtualmin)) `GPL-3.0` `Shell/Perl/Other`
 * Virtualization
   - [OpenVZ Web Panel](https://github.com/sibprogrammer/owp) - Web panel to control OpenVZ virtual machines.
 * Server