D-Level uses an open source-friendly business model called Dual Licensing. Dual licensing is a business model that allows software development companies to provide commercial software licenses for a fee to their customers, while at the same time offering their software under approved open source licenses.

As with companies like MySQL, Trolltech and Sleepycat, the guiding business principle at D-Level is one of fair exchange, or Quid pro Quo ("something for something").

From a licensing perspective, we have two different products depending on usage and distribution, though technically they have the same source code.

D-Level offers two main types of licenses: Public and Commercial.

Thanks to our licensing model, we are capable of producing superior software at a much lower cost than proprietary software vendors. Our licensing options include:

• The D-Level Commercial License, which allows you to provide commercial software licenses to your customers or distribute D-Level products-based applications within your organization. This is for organizations that do not want to release the source code for their applications as open source / free software; in other words they do not want to comply with the GNU General Public License (GPL).

• For those developing open source applications, the D-Level Public License allows you to offer your software under an open source / free software license to all who wish to use, modify, and distribute it freely. The Open Source License allows you to use the software at no charge under the condition that if you use D-Level products in an application you use or redistribute ,the complete source code for your application must be available and freely redistributable under reasonable conditions.

In their simplest form, the following are general licensing guidelines:

• If your want to distribute software for UNIX/Linux and Apple Macintosh and the software is licensed under either the GPL-compatible and Free Software License as defined by the Free Software Foundation or approved by OSI, then use our DPL licensed version,

• If you distribute a proprietary application in any way, and you are not licensing and distributing your source code under GPL, you need to purchase a commercial license ot the D-Level product.

• If you are unsure, we recommend that you buy our cost effective commercial licenses. That is the safest solution. Licensing questions can submitted for our advice, and we encourage you to refer to the Free Software Foundation or a lawyer as appropriate.

Commercially licensed customers get commercially supported product with assurances from D-Level. Commercially licensed users are also free from the requirement of making their own application open source.

For OEM's, ISVs, corporate, and government users, a commercial license is the proper solution because it provides you with assurance from the vendor and releases you from the strict requirements of the DPL license.

Nevertheless, you can test D-Level products under the DPL license and inspect the source code before you purchase a commercial license.