TOra is a Scripts software developed by Nathan Neulinger. After our trial and test, the software is proved to be official, secure and free. Here is the official description for TOra:

EditByMarydown: TOra is an open-source multi-platform database management GUI that supports accessing most of the common database platforms in use, including Oracle, MySQL, and Postgres, as well as limited support for any target that can be accessed through Qt's ODBC support. TOra has been built for various Linux distributions, Mac OS X, MS Windows, and UNIX platforms.

In addition to regular query and data browsing functionality, it includes several additional tools useful for database administrators and developers – which aims to help the DBA or developer of database application. Features PL/SQL debugger, SQL worksheet with syntax highlighting, DB browser and a comprehensive set of DBA tools.

Features
Handles multiple connections.
Asynchronus database communication. UI mostly responsive when accessing database.
Requires no installation on the database side to be fully functional.
Advanced SQL worksheet.
Code completion.
Explain execution plan.
Execution statistics.
SQL syntax highlighting.
Quick Menu for often used custom SQL.
Parse error location indication.
Chart visualization of result.
PL/SQL block parsing.
Schema browser.
Table & view editing.
References & dependencies.
Tab & tree based browsing.
Object & data filtering.
PL/SQL editor & debugger.
Breakpoints.
Variable watches.
Line by line stepping.
Debugger SQL output viewing.
Syntax structure tree parsing.