>Hi guys.
>
>In this oportunity I want to know if anyone of you can help me to find a good open-source tool that allow me to create, design and develop an app. The tool is to be use in Linux.
>
>Any tip, please?
>
>Regards.

mmm.... You don't say what languages you are comfortable with.
Look at: http://home.xnet.com/~blatura/linapp6.html some links are broken, some tools are old (vi, emacs and others)

My Favorites:
Free a/o GPL:
KDevelop 3.x with QT 3.x and PostgreSQL 7.x, if you know C++. Runs under KDE 3.x Se KDE.org website.
Designer in QT3 from TollTech. )C++). A standalone that is often linked in Kdevelop for dialog design
(The 3.0 version is desired because it has data-aware widgets (controls).
Glade, if you know C
Visual TCl, an underated but very powerful scripting language. http://vtcl.sourceforge.net/
Python 2.x is a very nice OOP lanuage. http://www.python.org/
pForth http://www.softsynth.com/pforth/ Forth has been a favorite of mine for 20 years.
SmallTalk/X http://www.exept.de/sites/exept/english/Download/frame_version_4_1_3.html


Commerical:
Kompany.com
Kylix Open Edition, if you know Object Pascal (not open source, however)
http://community.borland.com/article/0,1410,27584,00.html
Java: VisualAge for Java 3.x (IBM) Forte, Sun, Eclipse, IBM.